In 'Completing The Analogous Pair', two words are given. These words are related to each other in some way. Another word is also given. The candidate is required to find out the relationship between the first two words and choose the word from the given alternatives, which bears the same relationship to the third word, as the first two bear.
Assertion (A) : Cotton is grown in alluvial soils.
Reason (R) : Alluvial soils are very fertile.
Alluvial soils comprising of silt and sand carried down by the rivers, are very fertile. However, cotton is grown in black soil that suits its mineral requirements.