正确答案: B

+3

题目：亚硝酸钠（NaNO2）是一种工业用盐，外观酷似食盐，人若误食，会引起中毒。亚硝酸钠中氮元素的化合价是（ ）

解析：B

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举一反三的答案和解析：

[单选题]DWhen I was twelve years old, my family were the first black people to move into an all white part of Grand Rapids, Michigan. Many of our new neighbors weren’t very welcoming. Some of them said angrily that we should return to where we came from. The children sometimes threw stones at me or drove me home from school.

they had different skin colour

[单选题]下列句子没有语病的一项是（2分）

有没有正确的环保观， 低碳生活能否实现的关键。

[单选题]如果一个数的平方与这个数的差等于0，那么这个数只能是（ ）

0或1

[单选题]9．I think doing the dishes _________ ．

is boring

[单选题]Theplane______whenwegottotheairport.

hadtakenoff