The answer is (A).
PERMUTATIONS AND COMBINATIONS
To be successful with combinations and permutations questions like Example
8, you have to remember the relevant formulas.
PERMUTATIONS AND COMBINATIONS FORMULAS
The number of permutations of n distinct objects is n! = n(n − 1)(n −
2)···(3)(2)(1)
The number of permutations of n objects, a of which are
indistinguishable, b of which are indistinguishable, etc., is
The number of permutations of n objects taken r at a time is
The number of combinations of n objects taken r at a time is