Both topic and system should be entered, but this is not essential. The subcategory variable does not need to have an input but if it does not it will be assigned to the '?' grouping. The subcategory variables allow the quiz to be listed more appropiratley. For example a Urinary Quiz will be listed under the system (Urinary) but will then be listed under the subcategory 'A' (for anatomy).
Example page: Urinary Anatomy & Physiology Quiz
For a quiz on the pathology of the cardiorespiratory system.
For a quiz on the anatomy and physiology of the urinary system.
For a quiz on infectious diseases on viruses.
For a quiz on infectious diseases on tuberculosis.