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

问题补充：

—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

答案：

A. are

B. used to have

(答案→)C. used to be

D. 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。