Six chairs are in a line. Chairs 1, 3, 5 are blue. Chairs 2, 4, 6 are red. Two people sit down such that neither sits on a red chair and they are not adjacent. How many valid pairs of seats are there?
✓ Correct Answer: Option A
Blue chairs: 1, 3, 5. Not adjacent pairs: {1,3} adjacent ✗, {1,5} not adjacent ✓, {3,5} adjacent ✗. Only 1 valid pair: {1, 5}.