下列炎症因子中引起支气管哮喘的主要是()。
A.前列腺素类
B.血小板激活因子
C.白三烯类
D.组胺
E.以上都是
参考答案:C
We used to see each other ________,but I haven't heard from him since last year.(2012·辽宁)
A.especially
B.regularly
C.particularly
D.approximately
PIM-SM的特征有()
A.独立于单播路由协议
B.使用现存的单播路由表
C.嫁接与剪枝现象
D.依赖于无类单播路由协议