Given below are two statements. One is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A) :$ Knowing initial position $x_0$ and initial momentum $p_0$ is enough to determine the position and momentum at any time $t$ for a simple harmonic motion with a given angular frequency $\omega$.
Reason $(R) :$ The amplitude and phase can be expressed in terms of $x_0$ and $p_0$. In the light of the above statements,choose the correct answer from the options given below $:$

• A
  Both $(A)$ and $(R)$ are true but $(R)$ is $\text{NOT}$ the correct explanation of $(A)$.
• B
  $(A)$ is false but $(R)$ is true.
• C
  $(A)$ is true but $(R)$ is false.
• D
  Both $(A)$ and $(R)$ are true and $(R)$ is the correct explanation of $(A)$.