The experts were fully convinced that the animal ________a puma.
A:must be B:should have been C:can only be D:could only have been
我自己感觉应该是选择A
课文里面有一句话
The experts were fully convinced that the animal was a puma.
所以，我认为，D选项用完成时表示“本可以”或 “本可能”都不对
请知道答案的同学们帮忙下。