It's ________ you to sit there doing nothing at all while others are so busy.
A：stupid of
B：stupid for
C：wise of
D：wise for
给加下划线字选择正确的解释。
石猴喜不自胜，忽抽身便往外走。( )
求两条垂直的直线2x+y+2=0与ax﹣y﹣2=0的交点坐标．
