Let f : R → [0,p/2]be a function defined by f(x) = cot-1(X² + 4x + α² -α), then complete set of values of α for which f(x) is onto, is?
A. [(1-√17) /2, (1+√17) /2]
B. [-[infinity], (1-√17) /2] ∪ [(1+√17) /2, [infinity]]
C. [(1-√17) /2, (1+√17) /2]
D. None of these
