六氟化硫介质具有优越的（）性能。
A.绝缘；
B.耐腐蚀；
C.防潮；
D.灭弧。
参考答案：A, D
__________ sleep every night is important for teenagers. _________, loss of sleep can make you feel tired, and even cause you to put on weight.
A．A good amount of; As a matter of fact
B．A good number of; In truth
C．A large amount of; As matter of fact
D．Plenty of; In a fact
我国的动物种类多种多样，据统计，我国的脊椎动物有（ ）
A．2800种
B．6300种
C．360种
D．1600种
