治病必求于本
参考答案：本，这里指阴阳法则。人体疾病的形成是由于阴阳的失调，而治病的关键是协调阴阳，所以治病必求于本。
Look, read and complete.（补全下列对话）
Assistant: Can I help you?
Mom: Yes, please. A pair of 1.______ for my son.
Assistant: How about this pair?
Tom: Yes, I like 2.______. It's very pretty.
Mom: How 3.______ are they?
Assistant: They are 4.______ yuan.
Mom: OK. We'll 5.______ them.
酒精性肝病的严重程度与患者饮酒量呈正比。
for my son. 
yuan.