题干
The zoo keeper is worried because the number of visitors _______ smaller and smaller.
A：become
B：are becoming
C：is becoming
D：have became
答案(点此获取答案解析）
C
The zoo keeper is worried because the number of visitors _______ smaller and smaller.
A：become
B：are becoming
C：is becoming
D：have became
等于（ ）
