“My Heart will Go on” is once again popular among young people, ______ were often heard singing

it at parties.[ ]

A. who

B. which

C. they

D. that

下列哪项不是两栖动物分布范围小、种类小的原因（　　）

A．生殖和发育都离不开水

B．用肺呼吸

C．体温不恒定

D．幼体生活在水中