旋压
参考答案：
旋压成形是利用旋压机和模具以一定的速度共同旋转，并在滚轮的作用下使坯料在与滚轮接触的部位上产生局部变形，获得空心回转体零件的加工方法。
__________ sleep every night is important for teenagers. _________, loss of sleep can make you feel tired, and even cause you to put on weight.
A．A good amount of; As a matter of fact
B．A good number of; In truth
C．A large amount of; As matter of fact
D．Plenty of; In a fact
A．mgtgθ
B．mgsinθ
C．μmg
D．μmg
mgtgθ
mgsinθ