Question

---We’ve seen many more days of blue skies recently.
　 ---True. But back in 1998, ________ Beijing started its “Defending the Blue Sky”　　　　　program, the city only ________ about 100 days a year.　　

A．which, sees

B．that, saw

C．when, saw

D．and, seeing

Answer 1

C

回到1998年，那時北京開始了保衛藍色天空項目，這個城市大概只有一百天的晴空。考查非限制性定語從句，根據1998年，應為過去式。