A:草地沙化
B:洪涝灾害
C:乱砍滥伐
D:环境污染
科举制选拔官员主要凭靠( )
如图,△ABC中,BO,CO分别是∠ABC,∠ACB的平分线,∠A=50°,则∠BOC等于( )
在平面直角坐标系中,点P(2,﹣3)在( )
----How did he finish the work?----I hear that he did it __________.