Scientists Interested in Knowing the Best Way to Restore an Area

Scientists interested in knowing the best way to restore an area after a temporary road was built through it completed a study comparing two treatments: (1) restoring the contour of an area so that there was no longer a depression or cut-through where the road was previously and (2) simply abandoning the area to allow vegetation to return on its own. They wanted to know whether either or both of these treatments would return the aboveground vegetation and the belowground soil properties to their original state, as seen in a similar area where there had never been a road.
-In this experiment, the area that had never had a road is useful to the experiment because

A) at least three samples are necessary to have a valid experiment.
B) the area never roaded serves as a control for the experimental variables of recontoured and abandoned.
C) the researchers need to know what species of plants were common to all three areas.
D) since all three areas had existed for the same amount of time, the third area allowed time to be controlled as a variable.