energy we turn off the lights for Earth Hour on the last Saturday in MarchA. SavingB. To

问题补充：

energy, we turn off the lights for Earth Hour on the last Saturday in March

A. Saving

B. To save

C. Saved

D. Having saved

答案：

A. Saving

(答案→)B. To save

C. Saved

D. Having saved

解析：考查非谓语动词。题意：为节约能源，我们每年三月最后一个星期六关灯一小时。目的状语由不定式充当。故B项正确。