Restaurant owners have to know how food. [ ]
A. make
B. making
C. to make
D. makes
答案:C
上颌窦瘘修补术时,不适用的是()
A.腭侧瓣修补术
B.颊侧瓣修补术
C.唇瓣
D.颊、腭复合瓣
E.邻位瓣
闭锁原则是指以某种方法使一些元件强制发生互相作用,以保证安全操作。