19. A frictionless pendulum of length 3 m swings with an amplitude of 10∘. At its maximum displacement, the potential energy of the pendulum is 10 J . What is the kinetic energy of the pendulum when its potential energy is 5 J ?
(A) 3.3 J
(B) 5 J
(C) 6.7 J
(D) 10 J
(E) 15 J