对二维数组的正确说明是( )。(本题2.5分)
A. int a[ ][ ]={1,2,3,4,5,6};
B. int a[2][ ]={1,2,3,4,5,6};
C. int a[ ][3]={1,2,3,4,5,6};
D. int a[2, 3]={1,2,3,4,5,6};

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