自然条件下，病毒入侵肌体的三大重要门户是：（）
A、呼吸道
B、消化道
C、皮肤粘膜
D、饮用水
参考答案：A, B, C
--- Why was Mr. Li so happy this morning?
--- Because he was honoured with a(n) _____ for excellence in teaching.
A．present
B．gift
C．award
D．reward
简述液体疗法的基本方法。
