H2S在空气中的最高允许浓度为20千克/立方米。( )
参考答案:错
Later they discovered, ____ was news to him, that Pamela was the headmaster’s daughter.
A.that
B.which
C.what
D.who
MVC的分层体系结构是()。
A.Model/View/Components
B.Model/View/Controller
C.Model/View/Class
D.Modem/View/Controller