of结构的谓语动词单数还是复数取决于句子的主语.如:Three friends of mine are able to buy cars. One friend of mine is able to buy a car. 至于There are only 15 students in the classroom后,是用is 还是are 完全取决于句子的用意的逻辑推理题.你想,剩下的同学,如果大家都知道全班共16人,剩下1人,则可用is.如果剩下好多同学呢?当然用are啦.这句子就是看上下文了.希望能帮到你哦.