题目内容：
The zoo keeper is worried because the number of visitors _____ smaller and smaller. A.become
B.became
C.is becoming
D.have become
参考答案：
选择题：The zoo keeper is worried because the number of vi
- 题目分类：河南城建学院-水文与水资源工程-英语 C（一）
- 题目类型：选择题
- 查看权限：VIP
A.become
B.became
C.is becoming
D.have become