Suppose V1=，V2=，where R is the set of real numbers，+， and? are respectively addition and multiplication.Let f﹕R→R and f(x) = ex， which of the following propositions is true?

A、f is a surjective homomorphism from V1 to V2
B、f is an injective homomorphism from V1 to V2
C、f is an isomorphism from V1 to V2
D、None of the above