For a must be false we are trying to break this game. Here, the two easiest ways would be to break apart JG, or to force GK to be far apart.
I would first look for something that breaks up our block of JG, and the easiest way to break that would be to put one thing in the middle day that is neither j nor g. Thankfully, we have an answer choice that does just that in the form of c.
So deductions are important and helpful, but for must be false questions I really prefer to think about how to break the game.
