问题
选择题
Since then the number of people taking driving lessons ________ 20％.
A．has increased to
B．increases by
C．has increased by
D．have increased by
答案
答案：C
这题考查时态和介词的用法：时间状语是：since then，句子用现在完成时，increase by“增加了”，increase to增加到，句意是：自从那时起，上驾校的人的数量就增加了20%。选C。