问题
选择题
The zoo keepers is worried because the number of visitors __ smaller
and smaller.
A．become
B．became
C．is becoming
D．have become
答案
答案：C
考查主谓一致。the number of……的数目，谓语动词用单数形式。根据句意用现在进行时。句意：动物管理员担心游客的数量正在变得越来越少。