Let $A$ be a $4 \times 4$ matrix with real entries. Consider the sets


Suppose $K=J$. Then, which one of the following statements is necessarily true?

• Correct answer
  A

  $A^2=0$.
• B

  $A$ is symmetric.
• C

  $A$ is skew symmetric.
• D

  $A^2=A$.

Hence, the correct answer is option: 'A'.