车身上的活动铰链应经常保持清洁，并应涂上（）润滑油。
A、良好的
B、防腐
C、防垢
D、防老化
参考答案：B
下列属于植物病毒的是( )
A．流感病毒
B．烟草花叶病毒
C．T4噬菌体
D．肝炎病毒
－ _____ did your uncle leave his hometown?
－ He _____ for nearly twenty years. [ ]
A. When; has left
B. When; has been away
C. How long; has left
D. How long; has been away
