致病性大肠杆菌致病特点是
A．只引起肠道感染
B．不引起泌尿生殖器感染
C．内外毒素同时致病
D．外毒素可引起严重的毒血症
E．不引起败血症
参考答案：C
Which one of the followings does not limit the effective range of radar（）.
A.Pulse width
B.Pulse repetition frequency
C.Peak power
D.Target brightness
活塞式压缩机的优缺点？
