Idon't understand why the answer is d. what does answer choice d even mean? explain, !

Here's what I get.

Explanation:

Let's attack the problem by the process of elimination

(A) and (B) are wrong. The acceleration due to gravity is constant at a given location (9.80 m·s⁻²).

(C) is wrong. Air resistance decreases acceleration.

(E) is wrong. If the balls looked spherical, any deviation from perfection would have  only a small effect on the time to reach the floor.

(D) is the only option left. It means that if the balls are taking longer than expected to fall, the calculated value of the acceleration is too small.

They are probably using the formula,

h = ½gt²

If you insert the values for h and g, you get

That's a short time interval to measure with a stopwatch.

The experimental measurements of time could have varied by ±0.5 s.

The student could then have said that the calculated accelerations were not uniform.