Which of the following is correct?

Determinant is the number associated to a square matrix. The matrix in which the number of rows is equal to the number of columns is known as a square matrix.

If \(\det (A)=0\) for some \(3\times 3\) matrix \(A\), then \(A\) may be non- zero matrix

If a matrix has real entries, its determinant is real valued although eigenvalues may be complex. In this case the nonreal eigenvalues come as pairs of complex conjugates. If the matrix has complex entries, then the determinant can well be complex.