问题
We’ve seen many more days of blue skies recently —TrueBut 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
B:that, saw
C:when, saw
D:and, seeing
正确答案是：
同类题型
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