If \[\hat{a},\] \[\hat{b}\] and \[\hat{c}\] are three unit vectors, such that \[\hat{a}+\hat{b}+\hat{c}\] is also a unit vector and \[{{\theta }_{1}}\], \[{{\theta }_{2}}\] and \[{{\theta }_{3}}\] are angles between the vectors \[\hat{a}\], \[\hat{b}\]; \[\hat{b}\], \[\hat{c}\] and \[\hat{c}\], \[\hat{a}\], respectively, then among \[\theta _{1}^{{}}\],\[\theta _{2}^{{}}\]and \[\theta _{3}^{{}}\]

• A. all are acute angles
• B. all are right angles
• C. at least one is obtuse angle
• D. none of these