Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).

Assertion (A) : Millions of years ago, South American animals were overridden by North American fauna.

Reason    (R)  : Isthmus of Panama linked North America and South America.

In light of the above statements, choose the correct answer from the options given below.

Both (A) and (R) are true and (R) is the correct explanation of (A).  

Assertion (A) states that millions of years ago, South American animals were overridden by North American fauna. This is true. It occurred primarily during the Pliocene and Pleistocene epochs. During this period, North American fauna migrated into South America, resulting in significant changes to the fauna of South America.

Reason (R) states that the Isthmus of Panama linked North America and South America. This is also true. The formation of the Isthmus of Panama, which connected the two continents, played a crucial role in facilitating this event by providing a land bridge for the migration of animals between North and South America.