If a rainfall map shows an area as high rainfall, which additional question would be most useful?

Correct answer: Which geographical factor causes high rainfall there

The direct answer is C: the most useful question asks which geographical factor causes the high rainfall. A rainfall map tells us where rainfall is high, but a complete geographical understanding also asks why it is high. The reasoning is simple: first observe the rainfall pattern, then identify possible causes such as relief, winds, distance from the sea, season and pressure conditions. Mountains can force moist air to rise, and rising air may cool and produce rain. Option A, the language spoken there, is a cultural fact and does not explain rainfall. Option B, railway length, is a transport fact and is unrelated to the physical cause of rain. Option C is correct because it connects the observed map pattern with geographical explanation. Option D, the number of schools, is a social and educational fact, not a rainfall cause. A common mistake is to choose any question about the place; choose the question that explains the mapped pattern.