If $\quad f: R \rightarrow R \quad$ is defined by $f(x)=7+\cos (5 x+3)$ for $x \in R$, then the period of $f$ is

• A

  $2 \pi$
• B

  $\pi$
• C

  $\frac{\pi}{5}$
• Correct answer
  D

  $\frac{2 \pi}{5}$

Hence, the correct answer is option: 'D'.