Critical Reasoning

People in twenty different occupations were tested by a psychologist to determine how relaxed they were and how extroverted they were. The psychologist discovered that college teachers were the most relaxed and engineers were the least relaxed. The psychologist concluded that college teaching is a much more relaxing occupation than is engineering.

Which of the following, if true, most seriously weakens the psychologist's conclusion?

A. Most people who choose college teaching, but few who choose engineering, are relaxed people when they embark on their careers.
B. The college teachers had developed many interests to pursue in their leisure time, but the engineers had developed few such interests.
C. The college teachers had to meet more frequent but less rigid deadlines at work than did the engineers.
D. The college teachers and the engineers were approximately equally extroverted.
E. People who are very relaxed are also likely to be extroverted

OA A; I want to know what the problems are with options B and C. Do they not provide alternative explanations as to why teaching (on its own merit) is not a relaxing occupation-hence weaken?

Thanks.