Which of the following sets has the greatest cardinality?

All but (c) have the same cardinality
(A)

A:

(B) The set of all functions from

B: I think this is countable infinite

Its cardinality is, by definition,
(C) The set of all functions from

{

}

C: This is the answers but why?

Its cardinality is
(D) The set of all finite subsets of

D: Not sure how to determine cardinality here

For every subsets of with elements, so the set we're dealing with has cardinality
(E) The set of all polynomials with coefficients in

E: I think this countable infinite too.