液压元件安装前要用（）清洗，自制的重要元件应进行密封和耐压试验。
A.菜油
B.机油
C.煤油
D.汽油
参考答案：C
He was robbed last night, but _____ he didn't have much on him then. [ ]
A. fortunately
B. eventually
C. certainly
D. surprisingly
血栓闭塞性脉管炎的特征是（）。
A.没有间歇性跛行
B.游走性血栓性浅静脉炎
C.累及内脏
D.肢体皮肤正常
E.与酒精中毒有关
