Which of the books do you think____best among the bestsellers?

问题描述:

Which of the books do you think____best among the bestsellers?
A.sells B.is sold C.are sold D.sell
答案应该选A,为什么不是D?说明理由,

这些畅销书里面的哪一本卖得最好?
主语是一本书,当然用单数啦