For years,doctors____millions of patients' lives with the help of_英语解答

For years,doctors____millions of patients' lives with the help of microscopes.
A.have saved B.are saving C.will save D.Were saving为什吗选第一个呢

人气：440 ℃　时间：2020-02-03 09:33:04

解答

选项是A.
为什么选第一个,因为For years表示从过去算起到现在(还可以继续)“多年”.关于现在完成时的概念,到百度查询一下就清楚了.