he _____ research these three years,and he ___several discoveries this year.
问题描述：
he _____ research these three years,and he ___several discoveries this year.
a.has been doing ,made b.has been doing ,has made.
能否说明原因？
答
A,这三年来他一直做研究,这一年有了几个发现今年不是也可以用完成时吗如果后面有for this year, 可考虑B, 因为只是陈述今年的成绩，可直接用过去时this year 的前面能用for 吗for 在this year 前面有点牵强，但是一般完成时，时间长度前面有for 的居多。我的直觉告诉我选A, 因为B两个现在完成时感觉有点中式英语，过于强调语法的感觉。而且前面的and he 明显显示出不同的时态，若都用完成时，可直接说, he has been doing research these three year and has made several discoveries this year.