Step 1: Concept
A matrix $A$ is skew-symmetric if $A^T = -A$.
Step 2: Meaning
Taking the determinant of both sides: $\det(A^T) = \det(-A)$. Since $\det(A^T) = \det(A)$ and $\det(-A) = (-1)^n \det(A)$ for an $n \times n$ matrix, we have $\det(A) = (-1)^n \det(A)$.
Step 3: Analysis
If $n$ is odd, then $(-1)^n = -1$, which leads to the equation $\det(A) = -\det(A)$.
Step 4: Conclusion
The only number that equals its negative is zero ($2\det(A) = 0 \Rightarrow \det(A) = 0$).
Final Answer: (D)