Gregory is the owner of two clothing stores. He sells a variety of styles of clothing, but in general, he believes that having clothing with college logos in his stores would help people feel more school spirit. He is proposing an experimental study to examine his belief.

Among the following environmental factors, which does not have a long-term impact on the composition of a region's soil? a. kinds of crops grown b. types of fungi present c. topography of the landscape d. variety of species of mammals e. number of freezes occurring annually