若逆时针旋转90°记作+1，则-2表示（ ）。
顺时针旋转180°
平面磨削时，应采用硬度低、粒度粗、组织疏松的砂轮。
The children felt _________ because of the _______ result of the football match.
A．frustrated; frustrated
B．frustrating; frustrating
C．frustrated; frustrating
D．frustrating; frustrated
