The baby was born the evening April 3rd. [ ]
A. in; of
B. in; on
C. on; of
D. on; at
答案:C
如图所示的装置中,物体B和动滑轮总重10N,且恰好匀速下降.则A物体受到的摩擦力的方向和大小为( )
A.水平向右5N
B.水平向右10N
C.水平向左10N
D.水平向左5N
木香横切面中可见( )
A.油室B.油管C.油细胞D.乳管E.含橙黄色物的分泌细胞