Both the caribou and the reindeer
belong to the species Rangifer tarandus, but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend to spread far and wide.
(A) belong to the species Rangifer tarandus, but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend - Correct
(B) belong to the same species, Rangifer tarandus, but about 7,000 years of domestication in Eurasia have developed reindeer's tendency to circle in tight groups, which is different from caribou that tend - usage of which ; faulty comparison between tendency and caribou
(C) belong to the species Rangifer tarandus, but being domesticated in Eurasia for about 7,000 years has developed reindeer's tendency to circle in tight groups, and that is different from caribou tending - demonstrative pronouns without noun. you can only use these words as adjectives (that reason, these people) or as pronouns in constructions like 'that of...' ; faulty parallelism between tendency and caribou
(D) are the same species, Rangifer tarandus, but about 7,000 years of domestication in Eurasia have developed reindeer's tendency to circle in tight groups, while the tendency is for caribou -same issue with ARE vs. 'belong to' ; idiomatic usage problem with 'the tendency is for...': proper usage is 'X has a tendency to VERB'
(E) are the same species, Rangifer tarandus, but being domesticated in Eurasia for about 7,000 years has developed the reindeer's tendency to circle in tight groups, which differs from caribou tending - ARE the same species isn't acceptable ; usage of which to refer to tight groups ; bad parallelism between tendency and caribou
Answer A
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long