Question

【题目】You can save electricity by _______ the lights when you leave a room.
A.turn up
B.turning on
C.turn off
D.turning off

Answer 1

【答案】D
【解析】句意：你可以通过离开房间关灯来节约用电。A. turn up开大；B. turning on 打开； C. turn off 关上；D. turning off关上。依据句意，排除A,B；by为介词，后跟动词-ing形式。所以答案是D。