Given below are two statements: one is labelled as Assertion $(A)$ and other is labelled as Reason $(R).$
Assertion $(A):$ Electromagnetic waves carry energy but not momentum.
Reason $(R):$ Mass of a photon is zero.
In the light of the above statements,choose the most appropriate answer from the options given below:

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