—Who is that_____? —She's my sister.
A:boy
B:girl
C:man
如图所示,用滑轮组提升重物时,将重600N的物体在10s内匀速提升了2m,已知动滑轮重为100N(不计绳重和摩擦),则提升重物的过程中正确的是( )
2.15小时=____小时____分.
As is known to us all, taking exercise is b____ to our health.