A:3x−1
B:3(x−1)2
C:3x+1
D:3(x+1)
钢在熔化成钢水的过程中( )
—Is Jay on his way to the cinema?
—I regret ______ you that he can't come today.
遇到巨大声响时,要迅速张口,或闭嘴堵耳,这是为了维持大气压的平衡,保____ .