The figure below shows the structure of a mitochondrion with its four parts labelled $A, B, C$ and $D$. Select the part correctly matched with its function.

• A
  $D$ (outer membrane) - gives rise to inner membrane by splitting
• B
  $B$ (inner membrane) - forms infoldings called cristae
• C
  $C$ (crista) - possesses single circular $DNA$ molecule and ribosomes
• D
  $A$ (matrix) - major site for respiratory chain enzymes