The more specific the application of a rule the more restrictive the rule. A rule that allows a variable (X) to be placed only in the spot 2 or else 7 is very restrictive; similarly, a rule that makes it impossible for 5 of the 7 variables to be placed in a position is restrictive. You can divide the game board into two possible alternatives in both of these situations (assuming a single variable per position). Less restrictive rules would allow more possible game boards to exist and therefore would be less helpful in splitting the board.

Choice C is incorrect because it states that a statement is SHOWN to be false when all the statement is shown to be is logically inconsistent. It is plausible that the statement can be true and scientists can act in a logically inconsistent manner. He misses the point here and the analysis of the question is bad. There is a second statement that is taken to be true, the last two sentences.