The growth of public television in the past two decades ___ dramatic.
A. was
B. were
C. has been
D. have been
因为主词是the growth所以先去掉B和D
请问答案为什么是C不是A?

空格以前都是主词 持续了20年个人浅见时间放前面是在强调

https://www.ldoceonline.com/dictionary/past-> 2 ... 字意说明，注意这字样 "... until now"特别是第三和第二个例句。"was"不包含"now"，所以不是答案。下方例句找 Trafford ... has received ... in the pasttwo years ...现在完成式的时间区间涵盖范围是过去到现在（强调的是"现在"）

was是过去式.....表过去某一个时间点过去20年间〝持续成长〞 从过去到现在 用完成式

经查，这句在学测原文是阅读测验，为何你这里会变成文法题@@