A:2
B:4
C:23
D:43
If everyone ______to throw rubbish in the bins, our environment will become better and better.
如图1,在平面直角坐标系中,OA=7,OC=18,将点C先向上平移7个单位,再向左平移4个单位,得到点B,连接AB,BC.
如图中多边形的周长是____ 厘米.