question_answer

let \[\overrightarrow{a},\]\[\overrightarrow{b}\]and \[\overrightarrow{c}\] be three unit vectors such that \[\overrightarrow{a}\times (\overrightarrow{b}\times \overrightarrow{c})=\frac{\sqrt{3}}{2}(\overrightarrow{b}+\overrightarrow{c}).\] If \[\overrightarrow{b}\] is not parallel to \[\overrightarrow{c}\]then the angles between \[\overrightarrow{a}\]and \[\overrightarrow{b}\] is

A)  \[\frac{\pi }{2}\]                                   

B)  \[\frac{2\pi }{3}\]

C)  \[\frac{5\pi }{6}\]         

D)  \[\frac{3\pi }{4}\]

E)  None of these