A:what was she doing
B:what is she doing
C:what she was doing
D:what she is doing
则△OCD与四边形ABDC的面积比为( )
小麦的高杆和矮杆分别受基因D、d控制,则在卵细胞中控制矮杆的基因是( )
点P(﹣2,1)关于直线l:x﹣y+1=0对称的点P′的坐标是( )