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
正确答案B，也选对了。但是对于OG的解释表示不理解。。。
OG：The time line of this sentence, captred by the use of verb tenses, is of utmost importance. A combination of factors(in the past) encouraged farming traditions that are still with us today. The conditions for the use of the present perfect tense have endured are in place.