PPSC Past Papers & Solved MCQs

The iconic verse

Cyanobacteria are remarkable prokaryotes primarily known for their ability to perform nitrogen fixation. This vital biological process converts atmospheric nitrogen (N2), which is unusable by most organisms, into ammonia (NH3) and other nitrogenous compounds essential for life. This makes nitrogen available for plants and other organisms, playing a crucial role in the global nitrogen cycle.

• Oxygen (A) is produced by cyanobacteria through photosynthesis, not fixed.
• Carbon (B) is fixed by cyanobacteria as carbon dioxide during photosynthesis, but nitrogen fixation is their most distinctive elemental fixation process.
• Hydrogen (D) is an element but not directly "fixed" in the same metabolic context as nitrogen or carbon by cyanobacteria.

This problem involves a direct proportional relationship between time and the number of jumps. We are given that the girl jumps 820 times in 1 hour. To solve for the number of jumps in 30 minutes, we first recognize the relationship between the two time periods.

• One hour is equivalent to 60 minutes. Therefore, 30 minutes represents exactly half of an hour.
• To find the number of jumps in 30 minutes, we simply divide the total number of jumps in one hour by two: 820 jumps / 2 = 410 jumps.
• Distractors (A) 205, (B) 350, and (D) 600 are incorrect as they do not reflect this direct halving of the activity over half the time period.

Understanding common file extensions is fundamental for computer literacy. The file extension helps the operating system identify the file type and which program should open it.

• The correct file extension for a modern Microsoft Word document (since Word 2007) is .docx. This format is based on XML and is part of the Office Open XML standard.
• .ppt (A) is the extension for Microsoft PowerPoint presentations.
• .pdf (B) stands for Portable Document Format, a universal file format for presenting documents independently of application software, hardware, and operating systems.
• .txt (D) is used for plain text files, which contain unformatted text.

The Amazon Rainforest is globally recognized as the largest tropical rainforest and the largest moist broadleaf forest in the world, covering a vast area primarily across South America. Its immense biodiversity and ecological significance are unparalleled.

• The Congo Rainforest is the second largest, but significantly smaller than the Amazon.
• The Taiga Forest, also known as the boreal forest, is primarily composed of coniferous trees, not broadleaf, and is found in colder northern regions.
• The Sundarbans Forest is the largest mangrove forest, a specific type of wetland forest, not the largest moist broadleaf forest overall.

According to the United Nations, a person is considered an international migrant if they change their country of usual residence for at least 12 months. This definition helps distinguish between short-term visitors, such as tourists or business travelers, and individuals who are establishing a new residence in a foreign country for a more substantial period.

• Durations like 3 months or 6 months are typically considered short-term visits and do not meet the UN's threshold for an international migrant.
• While 24 months would certainly qualify, the specific minimum threshold set by the UN for statistical and policy purposes is 12 months.

Abdul Rehman Chughtai was a highly renowned Pakistani painter and artist, celebrated for his distinctive watercolor technique and his significant contributions to modern Islamic art. He is considered one of the pioneers of modern art in Pakistan and his work often drew inspiration from Mughal art and Islamic mysticism.

• He was not primarily known as a scientist, musician, or writer. His legacy is firmly rooted in the visual arts, where he developed a unique and influential style.

The diopter adjustment on a microscope is specifically designed to compensate for differences in vision between a user's left and right eyes. It adjusts the focus of one of the eyepiece lenses (ocular lens) independently, allowing both eyes to focus simultaneously without strain, ensuring a clear image for both.

• The objective lens provides the primary magnification and is not adjusted for individual eye focus.
• The stage is the platform where the specimen is placed and has no optical adjustment function.
• The light source provides illumination but does not affect the focus of the lenses for vision correction.

The physical parts of a computer that you can touch and see are collectively known as hardware. This includes all the tangible components that make up the computer system, such as the central processing unit (CPU), memory (RAM), storage devices (hard drive, SSD), motherboard, keyboard, mouse, and monitor.

• Software refers to the intangible programs and data that instruct the hardware on what to do.
• Firmware is a specific type of software embedded in hardware devices, but it is not the physical part itself.
• Malware is malicious software, a subset of software, and not a physical component.

This question tests knowledge of basic astrophysics and the composition of the universe. The abundance of elements is a key concept in understanding stellar formation and the origins of matter.

• Hydrogen (A) is by far the most abundant element in the universe, constituting approximately 75% of its elemental mass. It is the primary fuel for stars through nuclear fusion.
• Helium (C) is the second most abundant element, making up about 24% of the universe's elemental mass.
• Oxygen (D) and Carbon (B) are significantly less abundant, formed primarily in the cores of stars through stellar nucleosynthesis.

This question assesses knowledge of correct English prepositions, which are crucial for grammatical accuracy and clear communication. Prepositions often follow specific nouns or verbs to form idiomatic expressions.

• The correct preposition to use with the noun "respect" when indicating the object of that respect is "for". The phrase "respect for our leaders" correctly conveys the intended meaning of holding esteem or admiration towards them.
• Options (A) "on," (B) "at," and (C) "in" are grammatically incorrect in this context. While these prepositions have various uses, they do not form a standard or correct idiom with "respect" in this sentence structure.

Understanding the function of scientific instruments is fundamental in chemistry and physics. Each instrument is designed for specific measurements.

• A spectrophotometer (B) is the correct instrument. It measures the intensity of light absorbed or transmitted by a sample at different wavelengths. This allows scientists to identify substances and determine their concentrations based on their unique absorption spectra.
• A thermometer (A) measures temperature.
• A barometer (C) measures atmospheric pressure.
• A hygrometer (D) measures humidity or the amount of water vapor in the air.

The phrase 'A stitch in time saves nine' is a common English idiom. It means that it is better to deal with a problem immediately, because if you wait, it will become worse and take more effort to solve. The number 'nine' is the traditional and correct completion of this proverb, implying that a small effort now can prevent a much larger effort later. Options A ('Five'), C ('Seven'), and D ('Eleven') are incorrect as they do not complete the established idiom and would render the proverb meaningless.

Jane Austen is the celebrated author of the classic novel Pride and Prejudice, published in 1813. Her works are renowned for their social commentary and witty prose, focusing on the lives of the British gentry. Charlotte Bronte wrote Jane Eyre, while her sister Emily Bronte is known for Wuthering Heights. Charles Dickens authored many famous novels like Great Expectations and Oliver Twist. Therefore, Jane Austen is the only correct answer among the choices, as the other authors wrote different iconic works.

The correct conjunction to fill the blank is 'but'. 'But' is used to introduce a contrast or an exception. In this sentence, 'large' describes a positive or neutral attribute, while 'quite old-fashioned' introduces a contrasting or slightly negative attribute about the house. 'And' (A) would imply addition, 'so' (C) would imply a result, and 'because' (D) would imply a reason, none of which fit the intended meaning of presenting a contrasting characteristic.

The decline of the Mughal Empire is widely considered to have begun after the death of Aurangzeb in 1707. His long reign, marked by religious intolerance, costly wars, and expansionist policies, severely strained the empire's resources and sowed seeds of discontent. While Akbar (A) presided over a period of great prosperity, Shah Jahan (B) saw the empire's cultural zenith, and Bahadur Shah Zafar (D) was the last Mughal emperor, Aurangzeb's death marked the beginning of its fragmentation and eventual downfall.

The correct verb to complete the sentence is 'denied'. To 'deny' means to state that something is not true, which is appropriate when an accused person refutes making a statement. 'Opposed' (B) means to disagree with or resist, which doesn't fit the grammatical structure with 'having made'. 'Declined' (C) means to politely refuse or to decrease, which is incorrect in this context. 'Accepted' (D) is the opposite of the intended meaning, as it would imply admitting to making a statement.

Radioactivity is measured by a Geiger Muller Counter (C), often simply called a Geiger counter. This instrument detects and measures ionizing radiation, such as alpha, beta, and gamma particles. A Barometer (A) measures atmospheric pressure. A Hygrometer (B) measures humidity in the air. An Ammeter (D) measures electric current. Therefore, the Geiger Muller Counter is the specific device designed for detecting and quantifying radioactivity, making the other options incorrect.

The correct answer is Franklin D. Roosevelt. President Franklin D. Roosevelt, the 32nd U.S. President, coined the term "United Nations" in 1942 during World War II to describe the Allied countries fighting against the Axis powers. This name was later adopted for the international organization.

• Winston Churchill was the British Prime Minister and a key Allied leader, but he did not coin the name.
• Trygve Lie was the first Secretary-General of the United Nations, appointed after its formation.
• John F. Kennedy was a U.S. President much later and was not involved in the naming of the UN.