咽鼓管的生理功能包括()
A．保持中耳压力平衡
B．引流作用
C．对声刺激的保护作用
D．防声作用
E．防止逆行性感染的功能
参考答案：A, B, D, E
Don't make so much noise. The students _____ an English class. [ ]
A. are having
B. have
C. had
D. were having
压裂液对地层及填砂裂缝的伤害具体原因有哪些？
