Match the $\frac{C_P}{C_V}$ ratio for ideal gases with different types of molecules.

Molecule type	$\frac{C_P}{C_V}$
$A$. Monoatomic	$I$. $\frac{7}{5}$
$B$. Diatomic rigid molecules	$II$. $\frac{9}{7}$
$C$. Diatomic non-rigid molecules	$III$. $\frac{4}{3}$
$D$. Triatomic rigid molecules	$IV$. $\frac{5}{3}$

• A
  $A-IV, B-I, C-II, D-III$
• B
  $A-IV, B-II, C-I, D-III$
• C
  $A-III, B-IV, C-II, D-I$
• D
  $A-II, B-III, C-I, D-IV$