单选题
—I saw Anna in the library yesterday.—You______her; she is still abroad.
【正确答案】
B
【答案解析】[解析] “must have done”表示对过去事情的肯定猜测，其否定形式应用"can't/couldn't have done”，而不能用 mustn't。例如：He couldn't have been to that place alone，because he is just five years old!(他不可能自己一个人去那个地方，因为他才只有5岁!)