求问这句英文的句子结构

题目

求问这句英文的句子结构
A growing number of people have become fully aware that a global ecological crisis is just around the corner if we continue to neglect environmental protection.
主要是have become fully aware是怎么回事,为什么是become而不是became呢,这个到底是什么时态?

答案

have become fully aware,这个是标准的现在完成时
have + 过去分词,构成现在完成时