Let A be a 2 × 2 symmetric matrix with integer entries. Then A is invertible if
1. the first column of A is the transpose of the second row of A
2. the second row of A is the transpose of first column of A
3. A is a diagonal matrix with nonzero entries in the main diagonal
1
1 only
2
3 only
3
1 and 2 only
4
More than one of the above
5
None of the above