Answer: (n-1)!.
- A n!
- B (n-1)!
- C n!/2
- D n²
Correct answer: B. (n-1)!
Explanation: Circular permutation: fix one person to remove rotational equivalence. The remaining n−1 people arrange linearly in (n−1)! ways. Answer: (n−1)!.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections