单项选择题

According to some scientists' research findings, dolphins seldom sleep because _______.

A．of their stupidity
B．of their vulnerability
C．there are possible dangers in the ocean
D．aquatic mammals do not need sleep
<上一题 目录 下一题>
热门 试题

单项选择题
Compare with dreamless sleep, deep dream sleep is _______.
A．not the result of natural selection
B．less likely to appear to moneys
C．more protective to the animals
D．at a higher stage of evolution
单项选择题
Which of the following might be the best title for this passage
A．Evolution of Sleep.
B．Two Types of Sleep.
C．The Original Function of Sleep.
D．Animals and Sleep.
相关试题