$\textbf{First Method:}$
$13^{99}$ mod $17 = ?$
Find the Euler's totient function of $17$
If $'n'$ is prime number
$\phi(n)=n\left(1-\frac{1}{n}\right)$
$\phi(17)=17(1-\frac{1}{17})=16$
Find $99$ mod $16\equiv3$
Now find $13^{3}$ mod $17\equiv2197$ mod $17\equiv4$
__________________________________________________
$\textbf{Second Method:}$
$\dfrac{13^{1}}{17}\implies \text{Remander} = 13$
$\dfrac{13^{2}}{17} \implies \text{Remander} = 16$
$\dfrac{13^{3}}{17}\implies \text{Remander} = 4$
$\dfrac{13^{4}}{17} \implies \text{Remander} = 1$
$\implies \dfrac{13^{99}}{17} = \dfrac{(13^{4})^{24}\times 13^{3}}{17} = \dfrac{1\times 13^{13}}{17} = \dfrac{13^{3}}{17} \implies \text{Remander} = 4$
So, the correct answer is $4.$