When it comes to the civil war in Syria, the US government’s attitude towards it has experienced a(n)_______ change , which may have a positive effect on Syria present situation.

A．superior

B．superb

C．subtle

D．stubborn

橡胶衬里管道可输送工作压力和温度为（）的多种介质

A.0.6Mpa、50℃以下

B.0.6Mpa、80℃以下

C.0.3Mpa、50℃以下

D.0.3Mpa、80℃以下