6. A football player kicks the ball to try scoring a goal. When the ball reaches its highest point, which statement is true? (a) Its velocity and its acceleration are both zero. (b) Its velocity is not zero, but its acceleration is zero. (c) Its velocity is perpendicular to its acceleration. (d) Its accel-eration depends on the angle at which the ball was thrown. (e) None of statements (a) through (d) is true.