Amount of rain depends on:

The correct answer is B) Humidity in atmosphere. Rain forms when moist air rises, cools to its dew point, and water vapour condenses on particles to form droplets that grow heavy enough to fall. How much rain eventually falls depends on how much water vapour the air actually carries, and that is humidity.

• A) Air pressure: Low pressure encourages upward air movement, so pressure influences whether rain occurs and its type, but it does not set the amount directly.
• C) Water cycle: The water cycle is the overall circulation of water through evaporation, condensation, precipitation and runoff. It is the process in which rain occurs, not a factor that determines its quantity.
• D) Temperature: Warmer air holds more moisture, so temperature matters indirectly. It acts through humidity, which is why B is the more direct answer.

The core concept is the link between atmospheric moisture and precipitation. For Mains, this connects to monsoon variability and to climate change, since air holds roughly 7 percent more moisture for each degree Celsius of warming, which affects extreme rainfall.

Trap: Aspirants often pick temperature or air pressure because they are the standard drivers of weather systems. Ask what the amount of rain depends on directly, and the answer is the moisture content of the air.