PPSC Past Papers & Solved MCQs

The correct answer is Brain and Spinal Cord because these two primary structures form the main processing command center for the human nervous system.

• Step 1 (CNS Framework): The human nervous system is structurally divided into two main components: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
• Step 2 (Functional Overview): The CNS is entirely contained within secure skeletal cavities (the cranium protecting the brain and the vertebral column protecting the spinal cord). It acts to receive, process, integrate, and send out sensory information throughout the body.
• Incorrect Options:
  • Muscles and Bones is incorrect because they form the musculoskeletal system, which provides structural movement and support rather than neurological processing.
  • Blood and Lymphatic Vessels is incorrect because they comprise the circulatory and immune systems, handling fluid transport and defense.
  • Skin and Hair is incorrect because they make up the integumentary system, acting as an external protective barrier.

The correct answer is oxygen, acetylene and argon because a modern look at diverse industrial welding methods reveals that these three gases are the most widely used across gas and arc-shielding practices.

• Step 1 (Fact Check): Your original prompt marked oxygen and acetylene as the correct choice. However, the question specifically asks for gases used in 'different types of welding' (plural). Oxy-fuel torch setups utilize a mixture of oxygen and acetylene, while Gas Tungsten Arc Welding (TIG) and Gas Metal Arc Welding (MIG) heavily require inert shielding gases like argon to protect the weld puddle from atmospheric contamination. Therefore, option 3 provides the most comprehensive and factually accurate list for multiple welding types.
• Incorrect Options:
  • oxygen and hydrogen is incorrect because while oxy-hydrogen welding exists, it is limited to specialized micro-welding tasks and excludes dominant industrial options.
  • oxygen, hydrogen, acetylene and nitrogen is incorrect because nitrogen is rarely used as a primary torch fuel or shielding gas since it causes embrittlement in many metals.
  • oxygen and acetylene is incorrect because it only covers oxy-fuel gas welding, entirely ignoring modern gas-shielded arc welding processes that rely on argon.