如果a为有理数,那么下列各式一定为正数的是[ ]
A.2008a
B.a2008
C.a2008+1
D.|a|
答案:C
—— Now, where is my package?
—— ________. We'll be late for the train.
A.Come on
B.Forget it!
C.Don't worry.
D.Who knows?
铸铁中的合金元素()对石墨化起促进作用。
A、Mn
B、S
C、Si