题目选项分析

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.

Both the caribou and the reindeer 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 to spread far and wide.