The correct option is C 0
Given →α+→β+→γ=a→δ ............................................................(i)
→β+→γ+→δ=b→α ...................................................................(ii)
From (i), →α+→β+→γ+→δ=(a+1)→δ... .......................................................(iii)
From (ii), →α+→β+→γ+→δ=(a+1)→α ........................................................(iv)
From (iii) and (iv), we get,
(a+1)→δ=(b+1)→α .........................................(v)
Since →α is not parallel to →δ,
From (v), a+1=0 and b+1=0
From (iii), →α+→β+→γ+→δ=0