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，那时北京开始了保卫蓝色天空项目，这个城市大概只有一百天的晴空。考查非限制性定语从句，根据1998年，应为过去式。