常见的脉冲波形有()、()、()、()等。
参考答案:指数波;方形波;1/2正弦波;1/4正弦波
24.When Tom was very young ,he was ______ skateboarding, ______worried his parents a lot.
A.in; that
B.into; which
C.fond of; that
D.like; which
()是专门作为计算吨位和交纳费用依据的尺度。
A.船舶尺度
B.船型尺度
C.登记尺度
D.最大尺度