Why does rainfall decrease from east to west in the northern plains of India?

Correct answer: The Bay of Bengal branch loses moisture while moving westward

The direct answer is A: the Bay of Bengal branch of the southwest monsoon loses moisture as it travels westward across the northern plains. Moist winds first bring heavy rain to the eastern part of the region. As the winds move farther inland, they release rain repeatedly and therefore carry less water vapour. This creates a general east-to-west decrease in rainfall. Option A is correct because distance from the moisture source and progressive release of moisture explain the rainfall gradient. Option B is wrong because western India does not have more seas; the western interior is far from the main moisture source. Option C is wrong because eastern India is not completely dry; it receives substantial monsoon rain. Option D is wrong because the Himalayas extend across the north, not only in the east. The statement describes a general pattern, although local relief and other factors can modify it. Memory cue: “farther west, less monsoon moisture.”