Find Numbers $a$ And $b$ , Or $k$ , So That $f$ Is Continuous at Every Point

Multiple Choice

Find numbers $a$ and $b$ , or $k$ , so that $f$ is continuous at every point.
- $f(x) = \begin{cases}x^{2}, & \text { if } x \leq 4 \\ x+k, & \text { if } x>4\end{cases}$

A) $\mathrm{k}=12$
B) $k=20$
C) $k=-4$
D) impossible