A Particle in $x$ - $y$ plane

A particle is moving on a curve whose position at any time $t$ is given by $x(t)=f'(t)\sin(t)+f''(t)\cos(t)$ , $y(t)=f'(t)\cos(t)-f''(t)\sin(t)$ .

where $f(x)$ is a thrice differentiable function. Then the speed of the particle at time $t$ is given by:

A) $\left| f'(t)+f'''(t) \right|$

B) $\left| f'''(t) \right|$

C) $\left| f''(t)+f'(t) \right|$

D) $\left| f'(t)-f'''(t) \right|$