MCQOPTIONS
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| 1. |
Let S = {1, 2, ..., n}. The number of possible pairs of the form (A, B) with A ⊆ B for subsets A, B of S is |
| A. | 2n |
| B. | 3n |
| C. | n! |
| D. | \({\rm{\Sigma }}_{k = 0}^n\left( {\begin{array}{*{20}{c}} n\\ k \end{array}} \right)\left( {\begin{array}{*{20}{c}} n\\ {n - k} \end{array}} \right)\) |
| Answer» B. 3n | |