Please HELP! In many regions of the world, humans rely on underground water supplies called aquifers for fresh water. The amount of water an aquifer can store depends in part on the porosity of the rock or sediment in which the water is stored. Porosity is a measure of the amount of liquid that can be stored in a material and is related to the amount of empty space that exists between individual rock or sediment particles. A group of civil engineers wants to determine whether the porosity of surface soil affects aquifer recharge rates—the ability of aquifers to refill with water. The engineers conduct the following study to determine the porosity of the surface soil at various locations. The results of the study will then be compared with the recharge rates of the aquifer each location supplies with water.
1. Collect one 200-milliliter (mL) sample of soil from each of three locations.
2. Place each soil sample in a beaker.
3. Add 200 mL of water to each sample and allow the water to saturate the soil.
4. Measure the amount of standing water in each beaker (amount of water the soil did not absorb).
5. Determine the amount of water in the soil sample by subtracting the amount of standing water from 200 mL.
6. Divide the amount of water in the soil sample by 200 mL and multiply by 100 to determine the percent
porosity of the soil.
Which change to the experimental design would improve the reliability of the engineers’ measurements?

A.
using a liquid other than water to determine porosity

B.
using flasks instead of beakers

C.
testing single samples from more than three locations

D.
testing more samples from each location