How do I start eliminating combinations for this one?

Hi, for this question, we have no idea which of the four places C and F are in. This suggests that to solve this question, we will want to figure out what happens with our other two pilots and copilots. Looking at the pilots, we know that a and b must fly, although we can't necessarily determine who they fly with, since it's possible they fly alone. However, looking at the copilots, we know a little more. For D, we know that D cannot go with A ever, and in this question, D cannot go with C, so the only person that D can fly with is B. So, d must fly with b.