If $\overrightarrow{a}, \overrightarrow{b}, \overrightarrow{c}$ are unit vectors such that $\overrightarrow{a} + \overrightarrow{b} + \overrightarrow{c} = 0$. Then $\overrightarrow{a}. \overrightarrow{b} + \overrightarrow{b}. \overrightarrow{c} + \overrightarrow{c} . \overrightarrow{a}$ is equal to :

Question

( A ) $\frac{3}{2}$
( B ) $-\frac{3}{2}$
( C ) $0$
( D ) $2 [ \overrightarrow{a} \, \overrightarrow{b} \; \overrightarrow{c} ]$