If you're seeing these problems as part of your study of statistics, you should know that
C(n, k) = n!/(k!×(n-k)!)
where the "!" indicates the factorial, the product of all positive integers less than or equal to the given one.
Then C(7, 7) = 7!/(7!×0!) = 1/0!
You are supposed to know also that 0! ≡ 1, so C(7, 7) = 1.
This is the number of ways you can choose 7 objects from a pool of 7 objects without regard to order. (You can do it one (1) way: choose all of them.)
The appropriate choice is ...
B: 1
