如图所示,请在图中标出支点位置(用字母O表示),并作出动力臂(用L表示).
延长动力作用线,过支点作动力作用线的垂线段(即动力臂L).如图所示:
The teacher told his students that the earth _____ round the sun. [ ]
A. go
B. went
C. goes
D. had gone
A.A读数为零,V读数为零
B.A读数不为零,V读数为零
C.V读数不为零,A读数为零
D.V读数不为零,A读数不为零