A:30°
B:45°
C:90°
D:135°
彩电按原价格销售,每台获利60元;现在降价销售,结果彩电销售量增加一倍,获得的总利润增加了0.5倍,则每台彩电降价了( )元。
--- What about playing ______football after school?
--- I'm afraid I can't. I have to practice playing ______ piano,
③个位不够减,从____位退____,在个位上加____再减。