月经周期已建立后又中断6个月以上者，属于( )
A．病理性闭经B．原发性闭经C．继发性闭经D．生理性闭经E．以上都不是
参考答案：C
A hard-working man _____ become a great scientist, but a great scientist _____ be a hard-working
man.
A．can’t, can
B．may not, can
C．can’t, must
D．may not, must
How ______ your brother? [ ]
A. am
B. is
C. are
