Answer: 2n.
- A 2n
- B n!
- C n²
- D 2n-1
Correct answer: A. 2n
Explanation: Set x=y=1: (1+1)n = 2n. Sum of all binomial coefficients = 2n.
Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.
Concept context
Counting, arrangements, and selections