调制解调器是按被调制参数进行分类，属于线性调制的应（）。
A.不在下述选项中
B.是调频
C.是调相
D.是调幅
参考答案：D
— Michael was late for Mr. Smith's oral class this morning.
— _________? As far as I know, he never came late to class.[ ]
A. How come
B. So what
C. Why not
D. Guess what
The goods which do not pass through the territory by land but call for a change of the means of transport at a place with a Customs establishment is defined as （）.
A. transit goods
B. transhipment goods
C. through goods
D. import and export
