AB=(3,4)-(1,2)=(2,2).
— It’s time to go to bed, Mary.
— Oh, Mum, I won’t go to bed _____ I have finished my homework.
A.after
B.until
C.since
D.because
经常进行冷水浴,对人体有()的良好效果。
A.防止动脉硬化
B.减少胆固醇沉积
C.消耗皮下脂肪
D.消除疲劳