问题补充：
一How can we reduce C02 in our home?
一It’s easy． off your TV or computers when you’re not using
them and you’ll greatly reduce it．
A. Turn
B. To turn
C. Turning
D. Turned
答案：
(答案→)A. Turn
B. To turn
C. Turning
D. Turned
解析：考查固定句型。固定句型：祈使句+连词+陈述句=If条件句，主句。本题Turn off your TV or computers when you’re not using them and you’ll greatly reduce it．=If you turn off your TV or computers when you’re not using them, you will greatly reduce it.故A正确。
