单项选择题
A．half-brain sleep is found in all kinds of birds B．half-brain sleep is characterized by accelerated brain waves C．birds can control their half-brain sleep consciously D．birds always sleep with the whole of their brain at rest
A．for children to take advantage of their parents by using a foreign language B．to expose children to a foreign language after they can speak English C．to combine language lessons with sports games D．for children to learn several languages at the same time
A．The American ship eventually found a port and dumped its garbage before it returned home. B．Throwaway societies don’t need to transport their refuse and garbage to incinerator because they have a lot of space to put them. C．The wandering ship with garbage reflected the fact that garbage problem became very serious. D．The huge populations of rats swarm through poor neighborhood in many Western European countries because the garbage is thrown into the open dumps.