If two out of the three vectors are unit vectors. $\overrightarrow{a} + \overrightarrow{b} + \overrightarrow{c} = 0$ and $2(\overrightarrow{a} . \overrightarrow{b} + \overrightarrow{b} . \overrightarrow{c} + \overrightarrow{c} . \overrightarrow{a} ) + 3 = 0$, then the third vector is of length :

Question

( A ) 0 unit
( B ) 2 unit
( C ) 3 unit
( D ) 1 unit