皮皮学，免费搜题
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【多选题】
腐殖质形成稳定金属络合物的标志是( )A.
PH 值升高
B.
PH 值降低
C.
溶液酸性增强
D.
溶液酸性减弱
拍照语音搜题，微信中搜索"皮皮学"使用
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】若a=1- 2 ，先化简再求 a 2 -1 a 2 +a + a 2 -2a+1 a 2 -a 的值．
【单选题】听力原文：W: What size do you wear? M: A twelve. W: Oh, you're lucky. I have just the right size in store. Here it is. Why don't you try it on? Where does the conversation probably take place?
A.
In a clothing store.
B.
At the woman's home.
C.
In the sitting room.