The chart shows the movement of a ball after several seconds. column a is on the x-axis, and column b is on the y-axis. which titles should replace a and b? column a should be "time," and column b should be "position." column a should be "position," and column b should be "time." column a should be "velocity," and column b should be "speed." column a should be "speed," and column b should be "velocity."