OG13 71题求助！

清月依云

71. Alongthe major rivers that traverse the deserts of
northeast Africa, the Middle East, and northwest
India, the combination of a reliable supply of water
and good growing conditions both encouraged
farming traditions that, in places, endure in at least
6,000 years.

(A) good growing conditions both encouraged
farming traditions that, in places, endure in


(B) good growing conditions encouraged farming
traditions that have, in places, endured for

(C) of good growing conditions have encouraged
farming traditions that, in places, endured for


(D) of good growing conditions both encouraged
farming traditions that have, in places, endured


(E) of good growing conditions encouraged farming
traditions that have, in places, been enduring
for


答案是B，我选了E。
不太明白为什么不能加of然后同样从属于combination啊。然后have been enduring怎么错了，后面不是一个时间at least 6000 years...

flonacui

the combination of                  a reliable supply of water and good growing conditions
是直接后面那两个平行 the conbination of已经平均分配到了and的两部分当中 所以不需要再写出of 多余

at least 6000 years是现在完成时的标志 而且前面有个endured证明动作已经结束了 用have been enduring好像动作还在继续

清月依云

谢谢亲啦！！