神经衰弱的最主要症状是（）。
A.易疲劳
B.易激惹、兴奋
C.睡眠障碍
D.头昏、头痛
参考答案：A
某物质在空气中燃烧有二氧化碳产生，则该物质可能是
A．H2 B．S C．CH4 D． ．
Despite his great efforts,he ______unsuccessfully after all.
A．ended in
B．ended with
C．ended up
D．turned out
