A collection of condensed suspended dust particles in the air constitute

Analyze the question: The question asks what we call a collection of condensed particles suspended in the air, where the condensation forms around dust particles.

Explain the concept: Water vapour in the air condenses onto tiny dust particles (condensation nuclei). What we call the result depends on where it forms and how dense it is:

• Cloud: condensed water droplets on dust particles suspended high in the atmosphere.
• Fog: the same process, but at ground level, with very low visibility (under 1 km).
• Mist: similar to fog but thinner, with visibility greater than 1 km, also near the ground.
• Rain: droplets that have grown heavy enough to fall.

Step-by-step reasoning:

1. The question says "condensed" particles, so condensation has occurred.
2. The particles are "suspended in the air", so they are not falling. This rules out rain.
3. No mention is made of ground level or reduced visibility, so fog and mist are not the focus.
4. The general description of condensed droplets suspended in the air (high up) is a cloud.

Possible concern: Fog and mist are technically also suspended condensed droplets, but they are specifically defined as occurring near the earth's surface. Since the question gives no such detail, the most general answer is cloud.

Answer: A. Cloud

Exam tip: Remember the ladder: Cloud = high up, Fog = ground level and thick, Mist = ground level and thin, Rain = falling. If a question doesn't mention the ground or visibility, go for the general term, "cloud".