Instruction: Identify the assumptions that must hold for the statement to be valid, then choose the correct option. Statement: The Himalayas act as a natural barrier that prevents the monsoon winds from reaching the northern plains, thereby creating a dry region in the rain shadow area. Assumptions: I. The Himalayas prevent monsoon winds from reaching certain areas. II. The rain shadow effect leads to dry conditions in specific regions. III. Monsoon winds are the sole cause of rainfall in the northern plains.

Correct — A.
Rule: an assumption is what the statement cannot stand without.
Negate it: if the statement then collapses, the assumption is implicit.

I is implicit: deny it and the Himalayas stop the monsoon winds nowhere, so the barrier claim fails.
II is implicit: 'a dry region in the rain shadow area' only makes sense if a rain shadow brings dry conditions.

III is not: the statement still stands if the monsoon is not the sole source of rain.
Only I and II → option (a).

Why the others are wrong

• (b)
  Only II and III are implicit — Only II and III drops I, which the statement itself asserts, and takes in III. The statement never needs the monsoon to be the sole source of rain.
• (c)
  Only I is implicit — Only I leaves out II. 'Thereby creating a dry region in the rain shadow area' takes for granted that a rain shadow means dry conditions.
• (d)
  All assumptions are implicit — All takes in III, but the word sole claims more than the statement does. Deny III and the statement still stands.

In a statement–assumption item, an assumption is an unstated premise the statement depends on. The working test is negation: deny the assumption and ask whether the statement still makes sense.

An absolute word such as sole claims a lot. Test it by negation rather than rejecting it on sight: 'monsoon winds are not the only source of rain in the plains' leaves this statement standing, so III is not needed.

Key facts

• Negation test: if denying an assumption makes the statement collapse, the assumption is implicit.
• A rain-shadow area lies on the leeward side of a mountain range and receives little rain.
• Assumption III fails on the word sole: the statement never claims the monsoon is the only source of rain.

Common traps

• Rejecting I because the statement already says it: the statement cannot stand without it, and the key counts it implicit
• Accepting III because monsoon rain matters to the plains, when 'sole' claims far more
• Answering from geography rather than from the statement as printed

No directly related past PYQ was found.