Figure shows three vectors $\mathrm{p},\mathrm{q}$ and $\mathrm{r}$, where C is the mid-point of AB. Then, which of the following relation is correct?

$\mathrm{OB}+\mathrm{BC}=\mathrm{r}$

q + BC = r

OA + AC = r

p + AC = r

Adding these two equations, we get p + q=2r, AC and BC are equal and opposite vectors.