Professor Knight has noticed that students who guess on her multiple-choice tests are significantly more likely to choose answer choice C instead of A, B, D, or E. Basing her judgment on the fact that a variety of students from different social groups and backgrounds all do this, she has concluded that this tendency was acquired from her colleague Professor Leigh' s habit of predominantly using C as a correct answer choice, rather than students' natural tendency to choose the middle letter. Professors Knight and Leigh are the only professors who give multiple choice tests in the required classes of the first and second year. Which of the following, if true, would most strengthen the conclusion drawn by Professor Knight? ["Professor Knight's first-year students do not pick C more than any other letter, but her second-year students, who have all taken the same required classes, do.", 'She has noticed that students tend to choose C only at her current school, rather than having noticed this tendency throughout her career.', 'The students are required to take the same classes during their first year, but, with the exception of one required lecture, can choose their electives during their second year.', 'Professor Leigh has a similar theory and believes that Professor Knight is the cause.']