网络中所采用的安全机制主要有:()。
A.加密和隐蔽机制
B.认证和身份鉴别机制
C.路由控制
D.冗余和备份
参考答案:A, B, C
It took Andy two hours ____ his homework yesterday evening and I spent ____ mine. .
A.doing; less time finishing
B.doing; more time to finish
C.to do; more time to finish
D.to do; less time finishing
患者,女性,32岁。诊断为急性龈 * * 炎。检查示患牙有轻度叩痛,提示患者( )
A.龈 * * 下方牙周膜有炎症和水肿B.有急性根尖周炎C.有慢性根尖周炎D.有牙周脓肿E.以上均不是