Only in that way _____ find out how this kind of animal lived and then finished the research on tim
A.could theyB.they couldC.were they able toD.they were able to选哪个？为什么？
参考答案:Only in that way..需要用倒装 首先排除 B,D
be able to do 强调有能力去做什么事情
could can的过去式 能做什么，能够
C
只有通过这样的方式他们才能够了解这种动物是怎样生活的，最后才能完成对其的研究。