. By the year 2020 scientists _____ a lot of research on AIDS.A.had doneB.doC.are doingD.will have d

题目简介

. By the year 2020 scientists _____ a lot of research on AIDS.A.had doneB.doC.are doingD.will have d

题目详情


. By the year 2020 scientists _____ a lot of research on AIDS.
A.had doneB.doC.are doingD.will have done
题型:单选题难度:偏易来源:不详

答案

D

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