The chart shows the movement of a ball after several seconds. a 2-column table with 4 rows. the first column labeled a has entries 0, 4, 8, 12, 16. the second column labeled b has entries 0, 2.5, 6, 8, 10.5. 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.”