润滑脂能形成具有一定密封作用的脂圈，可防止固体或流体污染物的侵入，有利于在潮湿和多尘环境中使用。
参考答案：对
It was a long joumey , but we _______arrived. [ ]
A. constantly
B. eventually
C. traditionally
D. occasionally
试述贾谊和《过秦论》（上）的思想内容。
