单项选择题
A．concentrate on B．apply for C．look out for D．appeal on
How many more decades will have to pass （） scientists s...
单项选择题How many more decades will have to pass （） scientists succeed in providing a cure for cancer？
A．when B．before C．since D．until
The disease beri-beri （）．A．kills large numbers of Easte...
单项选择题The disease beri-beri （）．
A．kills large numbers of Eastern peoples B．is a vitamin deficiency （缺乏） disease C．is caused by diseased deer D．can be caught from diseased chickens
According to the author, many teenagers think they are ...
单项选择题According to the author, many teenagers think they are brave enough to act on their own, but in fact most of them （）．
A．have much difficulty understanding each other B．lack confidence C．dare not cope with any problems alone D．are very much afraid of getting lost
