动脉导管未闭与室间隔缺损的鉴别要点是()
A.有反复呼吸道感染
B.生长发育落后
C.左心室增大
D.肺动脉瓣区第二音亢进
E.以上均不是
参考答案:E
— Who helped Li Lei with his English?
— , he learnt it by himself.
A.Anybody
B.Somebody
C.Nobody
D.Everybody
红外谱图在1600-1700cm-1有吸收峰,则可能含有几种什么基团?