如图,在平面直角坐标系中,菱形OACB的顶点O在原点,点C的坐标为(4,0),点B的纵坐标是−1,则顶点B坐标是
A:(2,1)
B:(1,−2)
C:(1,2)
D:(2,-1)
△+☆=30
△-☆=10
在下列消化道中,均无吸收功能的一组是( )
①口腔 ②咽 ③食道 ④大肠.
Busy as he is, he still comes by and picks me up at his c ____ .