1991 December PT3 Game#4 Forum

[epokei]

I am having a hard time to comprehend this problem.
Question#20, Why C3→B2 is the correct answer?
I know A can only fly plane 1 or 4, but it does not preclude B and C flying 1 or 4.
So, if C flies plane 3, C can still fly plane2 and whichever A flies plane 1 or 4, B can fly the rest of it.

I would really appreciate if anybody could help and point out what I am doing wrong.
Thank you.