In Britain the accent you speak with, the clothes you wear and the schools you attend are all markers that identify your social class.
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If the hold takes longer than anticipated, check back with the caller periodically, so they don’t feel as though they have been abandoned.
与直齿轮传动相比,斜齿轮传动更为平稳,重合度更大。
轮系中若含有圆锥齿轮、蜗轮蜗杆或齿轮齿条,则各轮转向只能用(画箭头 )的方法表示。
Food is the paramount ________________of people.