Arrange the following cities in decreasing order of the rainfall they receive from the south-west monsoons in summer months: 1. Allahabad 2. Kolkata 3. Delhi 4. Patna

Answer: Option A

The correct answer is Option A: 2, 4, 1, 3
Let's break down why by looking at how the South-West Monsoon affects each city:
Kolkata (2): Receives the highest rainfall among these cities.
    It's located closer to the Bay of Bengal, where the monsoon originates, meaning it gets hit early and hard.
Patna (4): Gets substantial rainfall, but less than Kolkata.
    The monsoon has travelled further inland by this point, losing some moisture.
Allahabad (1): Receives less rainfall than Patna.
    The monsoon is even weaker as it moves further west.
Delhi (3): Receives the least rainfall of the four from the South-West Monsoon.
    It's relatively far from the coast, and the monsoon currents have often dispersed or weakened by the time they reach Delhi.
So, arranging them from most to least rainfall gives us: Kolkata > Patna > Allahabad > Delhi, which corresponds to the order 2, 4, 1, 3.