误机旅客在航班规定离站时间以后要求退票，需支付的误机费是客票价的（）。
A．20%
B．30%
C．50%
D．10%
参考答案：C
That hazy（雾霾）weather has hit 104 cities in middle-east China lately makes citizens well aware of
______a terrible problem China is faced with.
A．what
B．how
C．which
D．that
目前常用的3.5英寸软盘片片角上有一带黑滑块的小方口,当小方口被打开时,其作用是______。
A．只能读不能写
B．能读又能写
C．禁止读也禁止写
D．能写但不能读
