Air Pressure is lowest in

The answer is D, Summer. From April to June, intense insolation heats the land surface. The air above it expands and rises, so surface pressure falls. Over northwest India this produces a well-marked thermal low, which helps set up the monsoon trough and draws moist winds inland from the Indian Ocean.

Why the others are wrong:

• Winter (A): Cold, dense air sinks over the northern plains and Central Asia, forming a high-pressure area. Pressure is at its seasonal maximum here, not its minimum.
• Spring (B): A transition season. Pressure is falling from winter highs but has not yet reached its seasonal low.
• Autumn (C): The post-monsoon period, when land cools and pressure begins to rise again toward winter.

Core concept: thermal low versus thermal high, and how seasonal pressure controls the monsoon. This links to the Indian Geography section and to Mains questions on the monsoon mechanism.

Trap: Candidates confuse pressure with temperature or assume cold weather means low pressure. Cold winter air is dense and heavy, so it produces high pressure.