降低人群对传染病的易感性最主要的措施是
A．自然感染B．隐性感染C．病原体变异D．人工主动免疫E．移入免疫人群
参考答案：D
——Mike, have you heard that Mr. Black knocked down a girl and hurt her badly yesterday morning.
——Yeah. He_____too fast to stop his car while the girl was crossing the street.
A．was driving
B．drove
C．had driven
D．would drive
带内信令
