A:①④
B:②④
C:②③
D:①③
如图所示,在匀速转动的水平转盘上,有一个相对于盘静止的物体,随盘一起转动,关于它的受力情况,下列说法中正确的是( )
一 I have made great progress in spoken English since last year.
一 Well done! I am sure you'll be good at it soon.
梯形的中位线长为15 cm,一条对角线把中位线分成3∶2两段,那么梯形的两底长分别为( )