问题
选择题
"Mary, turn off the water_________you are brushing your teeth. " "Sorry, I'll do it at once. "
A. until B. while C. during
答案
答案：B
题目分析：句意: 玛丽，当你刷牙时，关掉水龙头。对不起，我马上做。A. until 直到……为止，B. while 与……同时， C. during 在…..期间，据句意，故选B。