某药物的主要成分为C9H8O4(其它成分不含碳元素),已知该药物的含碳量为48%,则该药物中C9H8O4的质量分数为( )
A.40%
B.60%
C.80%
D.90%
答案:C
You _____ pay your library fines. If not, you _____ not be allowed to graduate.
A.may; should
B.should; need
C.must; will
D.will; can
各级工会依法维护本单位从业人员在安全生产方面的()权益。