【题目】It was unbelievable that the little boy managed to reach the final destination, ________ drive a car.
A.let go
B.let down
C.let alone
D.let off

【答案】C
【解析】句意：令人难以置信的是那个小男孩设法到达了目的地，更别说开车了。let go (of) “放开，松手”；let down“放下，降低，使失望”；let alone“更别提，不干涉，更不用说”；let off“排放，免除”。分析选项可知C是正确的。