垂直向力牙合力最易引起牙周组织损伤。
参考答案:错
--How did he get infected?
--She ____the viruses without any protection.
A.exposed to
B.had exposed to
C.was exposed to
D.had been exposed
Oh, Janne, you’ve broken another glass. You ought ____when you washed it.
A.be careful
B.to care
C.have cared
D.to have been careful