A) $\left\{ \overrightarrow{\mathbf{r}} - \frac{1}{2}\left( \ \overrightarrow{\mathbf{a}}\mathbf{+}\overrightarrow{\mathbf{b}} \right) \right\}\left( \mathbf{\ }\overrightarrow{\mathbf{a}}\mathbf{-}\overrightarrow{\mathbf{b}} \right) = 0$
B) $\left\{ \overrightarrow{\mathbf{r}} - \left( \ \overrightarrow{\mathbf{a}}\mathbf{+}\overrightarrow{\mathbf{b}} \right) \right\} \bullet \overrightarrow{\mathbf{b}} = 0$
C) $\left\{ \overrightarrow{\mathbf{r}} - \frac{1}{2}\left( \ \overrightarrow{\mathbf{a}}\mathbf{+}\overrightarrow{\mathbf{b}} \right) \right\} \bullet \overrightarrow{\mathbf{a}} = 0$
D) $\left\{ \overrightarrow{\mathbf{r}} - \frac{1}{2}\left( \ \overrightarrow{\mathbf{a}}\mathbf{-}\overrightarrow{\mathbf{b}} \right) \right\} \bullet \left( \ \overrightarrow{\mathbf{a}}\mathbf{+}\overrightarrow{\mathbf{b}} \right) = 0$
Explanation
The correct answer is Option A: $\left\{ \overrightarrow{\mathbf{r}} - \frac{1}{2}\left( \ \overrightarrow{\mathbf{a}}\mathbf{+}\overrightarrow{\mathbf{b}} \right) \right\}\left( \mathbf{\ }\overrightarrow{\mathbf{a}}\mathbf{-}\overrightarrow{\mathbf{b}} \right) = 0$.
A detailed explanation for this question is being prepared.