-- That T-shirt with Yao Ming's picture on it ____ belong to David. He admires him a lot.
-- No, it _____ be his. He hates black color.
A:can; can't
B:may; needn't
C:must; mustn't
D:must, can't
已知函数y=Asin(ωx+φ)+B的一部分图象如下图所示。如果A>0,ω>0,φ<π2,则 ( )
下面能较为准确地估算12.98×7.09的积的算式是( )
上体育课时,体育老师发现同学们要用的篮球差气,于是他用打气筒给篮球打气,当篮球变圆后,仍继续给它打气,则篮球内气体的质量、体积、密度的变化过程是( )