支气管哮喘最常见的病因是（）
A.支气管-肺组织感染
B.空气污染
C.误吸入病毒
D.支气管阻塞
E.吸入性变应原
参考答案：E
初中生应该学会用恰当的方式与异性交往，要做到[ ]
A．注意影响，划清界限
B．光明磊落，无拘无束
C．落落大方，掌握分
D．互不往来，防止早恋
The new buyer identified a dozen new sources for the material, ___________ proved to be reliable．
A．most of them
B．most of which
C．most of whom
D．most of those
