亚急性感染性心内膜炎首要发生于下列哪种疾病()
A．风湿性心瓣膜病
B．室间隔缺损
C．动脉导管未闭
D．法洛四联症
E．以上均是
参考答案：A
能在短时间内使学生获得大量系统的科学知识的教学方法是（ ）
A．谈话法
B．讨论法
C．讲授法
D．练习法
— Hi, I ______ you for a long time.
— I ______ in Beijing. I've just come back. [ ]
A. hadn't seen; am
B. haven't seen; shall be
C. didn't see, will be
D. haven't seen; was
