下列命题正确的是
A:若a>b,b<c,则a>c
B:若a>b,则ac>bc
C:若a>b,则ac2>bc2
D:若ac2>bc2,则a>b
下列行为有利于提高空气质量的是( )
—Why did you leave that position?
—I ________ a better position at IBM.
下列运算,结果正确的是( )