Again, the two patterns for correct answers are that they will contradict a conditional statement that gave us, or it will contradict a possible inference we could have made. So when you read a must be false paragraph, you should still use your normal inference brain to look for what sort of possible things you could infer by combining two or more ideas. And remember that must be false doesn't mean which answer is making a bad unsupported inference. Illegal reversals and illegal negations are illegal inferences, but they're not contradictions. It's not about, hey, we didn't talk about that. Therefore, it must be false.