Assertion (A) : The monsoonal rainfall decreases as one goes towards the west and north-west in the Ganga plain. Reason (R) : The moisture-bearing monsoonal winds go higher up as one moves up in the Ganga plain. In the context of the above two statements which one of the following is correct ?

The correct answer is Option 3 because the Assertion (A) is factually correct, while the Reason (R) is scientifically incorrect.

Assertion (A) is true: The Ganga plain receives rainfall primarily from the Bay of Bengal branch of the South-West Monsoon. As these winds move from east to west (from the delta towards the upper plains), they gradually lose their moisture content through successive precipitation. Consequently, Kolkata receives more rainfall than Patna, which in turn receives more than Delhi.

Reason (R) is false: The decrease in rainfall is due to the depletion of moisture in the winds as they travel inland, not because they "go higher up." In fact, for rainfall to occur, air must rise and cool; however, the geographical trend here is defined by the distance from the oceanic source. There is no atmospheric phenomenon in the Ganga plain where winds consistently move to higher altitudes as they travel west that would explain a decrease in rainfall.