Which one of the following best states the main conclusion of the passage? A. Professional organizations of medieval canon lawyers probably only enforced ethical standards among their own members when provoked to do so by outside criticisms. B. Professional organizations of medieval civil lawyers seem to have maintained stricter ethical standards for their own members than did professional organizations of medieval canon lawyers. C. Professional organizations of medieval canon lawyers apparently served to defend their members against critics' attacks rather than to enforce ethical standards. D. The ethical standards maintained by professional associations of medieval canon lawyers were chiefly laid down in papal constitutions. E. Ethical standards for medieval canon lawyers were not laid down until professional organizations for these lawyers had been formed.