Which of the following statements is true?

• A
  $I_4O_9$ exists as $I^{3+}(IO_3^-)_3$.
• B
  $I_4O_9$ is a mixed oxide of $I(III)$ and $I(V)$.
• C
  Upon decomposition,$I_4O_9$ gives $I_2O_5$.
• D
  All of these statements are true.