Assertion $(A)$: Cyclohexane is the most stable cycloalkane.
Reason $(R)$: Cyclopropane and cyclobutane are less stable due to angle strain and torsional strain.
The correct answer is:

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