One strategy to answering a multiple-choice question is to a) be aware of negative wording b) only change your answer once c) mark the shortest answer d) always guess ''a''

The best answer of the choices above is: a) be aware of negative wording.

You should not be changing your answers at all (b) unless you are absolutely certain that you made a silly error in choosing your first answer. Length or brevity (c) of the answer should not determine its veracity. Never "always choose" a certain answer (d), there is no evidence that supports this increasing your odds if more correct answers.