A pendulum bob of mass m is suspended by a light inextensible string of length L . A constant horizontal force F is applied to the bob, starting from its lowest vertical position. What is the horizontal component of the displacement of the bob when the string makes an angle θ with the downward vertical?
(A) L(1−cosθ)
(B) Lsinθ
(C) Ltanθ
(D) Lcosθ