Mitochondria and chloroplasts:
$(a)$ Are semi-autonomous organelles.
$(b)$ Are formed by the division of pre-existing organelles. They contain $DNA$,but lack protein-synthesizing machinery.
Which of the following options is correct?

• A
  $(b)$ is correct,while $(a)$ is incorrect.
• B
  $(a)$ is correct,but $(b)$ is incorrect.
• C
  Both $(a)$ and $(b)$ are incorrect.
• D
  Both $(a)$ and $(b)$ are correct.