The displacement affect the amount of work done by the fact that more displacement implies more work.
Option B
<u>Explanation:</u>
Work can be defined as the "measure of energy transfer" that occurs when an object is moved over a distance by an external force which is applied in the "direction of the displacement".
Work can be formulated as,

From the above-mentioned formula, we can infer that Work is directly proportional to the displacement of the object.Therefore, more the work is more will be its displacement.
Answer: You can increase the weight, then test the speed, and make the weight normal and test the speed, and mark which one travels faster.
Explanation: This would test your hypothesis by comparing the speeds of the cars when more mass is added. Calculating the difference of the speed with more mass, and the speed with normal mass would give you your answer. A positive number would prove your hypothesis and a negative number would disprove it.
The answer is : C. reduce their input force
they put wax on their kayak to make their boat cut smoothly through the water, which make it able to obtain further distance with less input force, which will increase it's overall speed