Unit vector along `veca` is denoted by `hata(if |veca|=1,veca` is called a unit vector). Also `veca/|veca|=hata and veca=|veca|hata`. Suppose `veca,vecb,vecc` are three non parallel unit vectors such that `vecaxx(vecbxxvecc)=1/2vecb ` and `vecpxx(vecqxxvecr)=(vecp.vecr.vecq)-(vecp.vecq)vecr]`. Angle between `veca and vecb` is (A) `90^0` (B) `30^0` (C) `60^0` (D) none of these