—Look, there many birds around here, but now we hardly see them. What a pity!—Yeah! The ai

—Look, there many birds around here, but now we hardly see them. What a pity!
—Yeah! The air pollution has caused the problem!
A. are
B. used to have
C. used to be
D. use to be

A. areB. used to have(答案→)C. used to beD. use to be解析：句意：看，这儿四周过去有许多鸟，但是现在我们几乎看不到它们了。太可惜了。——是的，空气污染引起来这个问题。There be句型表示“某地(或某时)存在有某人(或某物)，而并非某地(某人、某物或某时)拥有什么东西”，句中有若干个名词作主语，动词be常与后面主语中的第一个名词在数上一致。have一般表示某人有某物。used to do sth过去常常做某事.结合语境可知选C。

这下我知道了