“笑气”（N2O）在医学上曾被用作麻醉剂，其中N元素的化合价是：

“笑气”（N₂O）在医学上曾被用作麻醉剂，其中N元素的化合价是：（）

A、-1 B、+1 C、+2 D、+3

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“笑气”（N2O）在医学上曾被用作麻醉剂，其中N元素的化合价是：

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