如图所示用滑轮组将重600N的物体在10秒内匀速提升了5 m，如拉力为400N，则下列各计算结果正确的是(   )

用如图①中的长方形和正方形纸板作侧面和底面，做成如图②的竖式和横式的两种无盖纸盒．现在仓库里有m张正方形纸板和n张长方形纸板，如果做两种纸盒若干个，恰好使库存的纸板用完，则m+n的值可能是（　　）

用所给词的适当形式填空

①I have two ____ (brother).

②There are two ____ (family) in the picture.  

③ The old man has no ____ (son) or ____ (daughter).

④ My ____ (father) sister is my aunt.

⑤In the photo his mother's ____ (parent) are on the left.