Assertion $(A)$: The boiling points of noble gases increase from $He$ to $Xe$.
Reason $(R)$: The interatomic van der Waals' attractive forces increase from $He$ to $Xe$.
The correct answer is:

• A
  Both $(A)$ and $(R)$ are true,and $(R)$ is the correct explanation of $(A)$
• B
  Both $(A)$ and $(R)$ are true,and $(R)$ is not the correct explanation of $(A)$
• C
  $(A)$ is true but $(R)$ is not true
• D
  $(A)$ is not true but $(R)$ is true