师生交往的类型分为单项交往类型、______和______。
参考答案：双项交往类型 多项交往类型
人体几种体液和代谢产物的正常pH如图所示：其中一定不表现酸性的是
A．胃液
B．尿液
C．唾液
D．血液
If you'd written earlier, I'd have known when you _____ to go on holiday.[ ]
A. want
B. have wanted
C. wanted
D. will want
