Renaissance

[vivekcall81]

During the Renaissance, scholars were uncertain as to the location of Troy, and by the eighteenth century many historians doubted that Troy had ever existed.
(A) doubted that Troy had ever existed
(B) doubt that Troy has ever existed
(C) were in doubt as to the existence of Troy
(D) were doubtful concerning Troy’s existence
(E) had doubts about Troy’s ever existing

PLease explain why D is wrong.

[sanyalpritish]

According to me A

[Ben Ku]

Please cite the source (author) of this problem. We cannot reply unless a source is cited (and, if no source is cited, we will have to delete the post!). Thanks.