已知方程①2x+y=0；②12x+y=2；③x2﹣x+1=0；④2x+y﹣3z=7是二元一次方程的是

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已知方程①2x+y=0；②

1

2

x+y=2；③x²﹣x+1=0；④2x+y﹣3z=7是二元一次方程的是（　　）

A：①②

B：①②③

C：①②④

D：①

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A

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