The homogeneous system \( Ax = 0 \) has only the trivial solution (i.e., \( x = 0 \)) if and only if the matrix \( A \) is non-singular, meaning its determinant is non-zero.
Step 1: Analyzing the properties of a singular matrix.
If \( A \) is singular, its determinant is zero, and the system \( Ax = 0 \) will have infinitely many solutions. But in this case, we are told that only the trivial solution exists. This implies that \( A \) must be non-singular, meaning its determinant is non-zero, and thus the correct statement is \( A \) is singular.
Step 2: Conclusion.
Hence, the correct answer is (A).