question_answer

Let \[\overrightarrow{a},\overrightarrow{b}\] are unit vectors and c is a vector of magnitude 2. If these three vectors are such   each one of them is perpendicular to the sum of the other two, then the value of \[|a+b+c|\] is

A)  \[\sqrt{8}\]   

B)                                     \[\sqrt{6}\]

C)  \[\sqrt{5}\]         

D)                                     \[\sqrt{3}\]