Let 0<α<2π be a fixed angle. If P=(cosθ,sinθ) and Q=(cos(α−θ),sin(α−θ)) , then Q is obtained from P by
a. clockwise rotation around origin through an angle α
b. anti-clockwise rotation around origin through an angle α
c. reflection in the line through origin with slope tanα
d. reflection in the line through origin with slope tan(2α)