Which one is the essential of Shunshui Tuizhou？ A: Relax shoulders, hips and knees along with exhalation. Be concentrated and regulate breath. B: Coordinate the forward movement of the upper limbs and extension and flexion of the lower limbs. C: Keep the upper torso upright and the head still. D: Dorsiflex the wrists as much as possible. E: Relax the hips and knees when you lift your forearms as if you are holding a ball.