The zookeeper is worried because the number of visitors____smaller and smaller.A.become B.became C.is becoming D.have become为什么不选D呢?“smaller and smaller”是越来越少,用现完,表示过去就开始减少了到现在越来越少了,

Question

The zookeeper is worried because the number of visitors____smaller and smaller.
A.become B.became C.is becoming D.have become
为什么不选D呢?“smaller and smaller”是越来越少,用现完,表示过去就开始减少了到现在越来越少了,也表示过去发生对现在的影响啊,为什么不用现完?

Answer 1

the number of 作主语时谓语动词要用单数,只有C对.
加油!不明白再问!