A.30~60 B.76~100 C.50~100 D.60~110
A.3 B.4 C.5 D.6
A.以堅(jiān)實(shí)平坦的塑膠地板為宜 B.以堅(jiān)實(shí)平坦的沙地為宜 C.以堅(jiān)實(shí)平坦的草地為宜 D.以堅(jiān)實(shí)平坦的水泥地為宜