最不可能的病因是
A．泌尿系梗阻性病变B．类风湿性关节炎C．齿周脓肿D．皮肤化脓性感染E．鼻窦化脓性感染
参考答案：B
— If I hadn’t been caught in the heavy rain, I could have been back by 7 o’clock.
— What a pity! Stella _______ here to see you.
A．is
B．has been
C．would be
D．was
凝汽器水位过高有什么害处？
