Assertion $(A)$: Helium has the lowest boiling point $(4.2 \ K)$.
Reason $(R)$: The forces that exist between helium atoms are weak dispersion forces.

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