汽油的理想组分是()
A、正构烷烃
B、异构烷烃和芳香烃
C、环烷烃
参考答案:B
下列对胃酸作用的叙述,错误的是()
A.激活胃蛋白酶原,提供所需的酸性环境;并使蛋白质变性
B.保护胃黏膜
C.抑菌、杀菌
D.有助于小肠铁和钙的吸收
Success as ______ by economic output bears no close relationship to human achievement.
A.decided B.achieved C.assured D.measured