If $D_1$ and $D_2$ are two $3 \times 3$ diagonal matrices,then

  • A
    $D_1D_2$ is a diagonal matrix
  • B
    $D_1D_2 = D_2D_1$
  • C
    $D_1^2 + D_2^2$ is a diagonal matrix
  • D
    All of the above

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