I. It is a rapid, constant and irregular motion of tiny particles. II. It gives evidence that tiny particles…

Analyze the question: You are asked which statements correctly describe Brownian motion.

Concept: Brownian motion is the random, zigzag movement of tiny visible particles (such as smoke or pollen grains) suspended in a fluid. The fluid can be a liquid or a gas. The motion happens because the fast-moving, invisible molecules of the fluid keep bombarding the particles unevenly from different directions.

Checking each statement:

• I. A rapid, constant and irregular motion of tiny particles. True. This is the basic description of Brownian motion.
• II. It gives evidence that tiny particles of matter called molecules exist. True. The visible particles can only be jolted about if there are much smaller, invisible molecules hitting them. This supports the molecular theory of matter.
• III. It takes place only in gases. False. It also occurs in liquids, for example pollen grains in water. Smoke in air is the gas example.
• IV. It gives evidence that molecules are in a constant state of random motion. True. The continuous, irregular movement of the particles shows that the molecules hitting them are themselves moving randomly all the time.

Correct statements: I, II and IV only.

Tip: Watch for words like "only" in JAMB statements. Brownian motion occurs in fluids, meaning both liquids and gases. Any option that says "only in gases" or "only in liquids" is wrong, which here eliminates every option containing III (A, B and C).