Statement $A: C_P - C_V = R$
Statement $B: \frac{C_P}{C_V} = 1.67$

• A
  Statement $A$ and $B$ are true for all ideal gases.
• B
  $A$ is true for all ideal gases and $B$ is true only for monatomic gases.
• C
  $A$ and $B$ are true for monatomic gases.
• D
  $A$ is true for all ideal gases and $B$ is true only for diatomic gases.