题目选项分析

Along the 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 encouraged farming traditions that have, in places, endured for at least 6,000 years.

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