Thanks for the question! So we assume exactly two stations stay open, which means four total have to close. So we know L and R can’t both be open, and N and R can’t both close. And M is related too. Thinking about their relations, these four could all be in or out. But that means P and Q can’t be in, because two of that set of four have to be in. So P and Q have to be out, and that makes (D) the answer.
Hope this helps! Feel free to ask any other questions that you might have.
