问题
选择题
I hate travelling by air__________ you usually have to wait for hours before the plane takes off.
A．because
B．though
C．until
D．unless
答案
答案：A
because因为；though 虽然，尽管；until直到；unless除非，如果不。句意：我讨厌乘飞机旅行，因为在飞机起飞前你必须等上几个小时。结合语境可知选A。
