81. 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

(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

(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

(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

(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

答案是A。但我觉得A有问题：after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend

1 为什么要用完成时态

2 为什么while前用完成时态，while后面却不用完成时态

3 reindeer应该用has ， 还是have

(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

(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

(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

(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

其他的错误更加明显，个人以为原文中的时态一般不会错，否则，无法准确的表达作者思路，毕竟时态本身究竟是完成时还是现在时只有有效性的差别。

both and已经表达了同一种的含义，后面就不能用same了,剩AC

C里面有个being不对，所以选A

现在时态好象已经不是GMAC喜欢的出题点了， 应该是说从7000年前到现在这个点为止，这样就可以用完成事态，reindeer是一个物种，和民族一样，用复述，while表转折，对后面的没有用完成，可能是由于作者想表示后面那个物种没有一个变化的过程，也就是说他们的习性还是以前的，没改变