A ball is thrown at an angle of 45 degrees above the horizontal. Which of the following best describes the acceleration of the ball from the instant after it leaves the thrower's hand until the time it hits the ground?
A) Always in the same direction as the motion, initially positive and gradually dropping to zero by the time it hits the ground
B) Initially positive in the upward direction, then zero at maximum height, then negative from there until it hits the ground
C) Always in the opposite direction as the motion, initially positive and gradually dropping to zero by the time it hits the ground
D) Always in the downward direction with the same constant value