1. The villagers --- natural water sources while they --- their crops. a. were using – watered; b. used – were watering; c. used – watered; d. were using – were watering

Перевод задания: Выберите правильные варианты.

d. were using – were watering. The villagers were using natural water sources while they were watering their crops. (Жители деревни пользовались природными источниками воды, пока поливали свои поля.)

Оба действия происходили одновременно и длились некоторое время, поэтому используется Past Continuous.