MCQ

$$\sum_{i=1}^nc=cn$$ $$\sqrt[asdf]{asdfasdf}$$ $$\begin{gather} \notag\\ \notag\\ \frac{2\sqrt{2\mu _{0}}}{\pi } \cdot \ \frac{{\textstyle \mathrm{M}}}{\mathrm{a}^{3}} \end{gather}$$