Which generation of computers introduced microprocessors?

The correct answer is Fourth. Microprocessors were introduced during the fourth generation of computers (approximately 1971 to the present). The invention of the microprocessor (such as the Intel 4004) allowed entire CPUs to be placed on a single chip, leading to the development of personal computers. Among the options:

• First: Used vacuum tubes.
• Second: Used transistors.
• Third: Used integrated circuits (ICs), but not microprocessors yet.
• Fourth: Correct; this generation introduced microprocessors.

Hence, the correct answer is "Fourth".