Suppose V1=＜R,+＞,V2=＜R, ·＞,where R is the set of real
numbers, +and · are respectively addition and multiplication. Let f: R→R and
{(x) = 10x, which of the following propositions is true ( )
A．f is an injective homomorphism from V1 to V2 B．f is a surjective homomorphism from V1 to V2 C．f is an isomorphism from V1 to V2 D．none of the above