英语38.Dr.Smith has ten more years before retirement.By then he ______ a cure for the disease.
问题描述：
英语38.Dr.Smith has ten more years before retirement.By then he ______ a cure for the disease.
38.Dr.Smith has ten more years before retirement.By then he ______ a cure for the disease.
A.has discovered B.must have discovered C.had discovered D.will have discovered
为什么
答
D.首先 then 指的是 ten years later,很明显那是将来的时间 而答案中只有一个将来时态 就是D