In the Late 1800s, Louis Pasteur Was Searching for a Vaccine

In the late 1800s, Louis Pasteur was searching for a vaccine for anthrax in livestock. One French veterinarian had a local reputation for being able to cure anthrax by applying oils and wrapping the animal in cloth to induce a fever. Pasteur also knew that some animals recovered well on their own when left untreated. Pasteur tested the effectiveness of the local veterinarian's methods by injecting four cattle with anthrax bacteria. He then directed the veterinarian to perform his procedures on two cattle. The other two cattle were left alone. What is the rationale for Pasteur's experimental design?

A) Two cattle represent a test of the veterinarian's hypothesis; two represent a test of Pasteur's hypothesis.
B) Two cattle represent a test of the treatment; two serve as a control to determine the likelihood of survival without treatment.
C) Two cattle represent a test based on inductive reasoning; two serve to test deductive reasoning.
D) The two cattle that are treated are the only test being conducted; the other two cattle serve no purpose beyond representing all the untreated cattle in France.
E) The two cattle not being treated were just a whim on Pasteur's part.