颈静脉怒张常见于()
A．心包积液
B．右心衰竭
C．左心衰竭
D．纵隔肿瘤
E．甲状腺肿大
参考答案：A, B, D
It was not until then that I came to know that knowledge _______ only from practice.
A．had come
B．has come
C．came
D．comes
下列手段中属于正强化的内容是( )。
A．批评B．降级C．提升D．罚款
