单项选择题
A.45°B.55°C.50°D.60°
A.1/3B.1/4C.1/5D.1/6
A.5:4B.6:4C.7:5D.6:5
A.1/7B.1/8C.1/9D.1/10
微信扫一扫,加关注免费搜题