平型带交叉式带传动,两轮()。
A.转向相同,线速度相等
B.转向相同,线速度不等
C.转向相反,线速度相等
D.转向相反,线速度不等
参考答案:C
—Now computers _____ in many ways.
—I agree with you. I think they are the most useful inventions in the world. [ ]
A. used
B. use
C. are used
D. were used
在长度测量的实验中:
(1)首先要观察刻度尺的 ______、______和 ______.
(2)刻度尺在测量中摆放时,零刻度要对准 ______、尺的位置要 ______.
(3)在读数时,视线要 ______刻度线.
(4)当所用的刻度尺的零刻度有磨损,而其它部分没有损坏的情况下,刻度尺依然可以测量物体的长度,但应该怎样做?