Let $f: Z^+ \rightarrow Q$ is a mapping from the set of positive integers to the set of complex numbers, defined as $f(x)=\frac{x}{(2x+1)}, x ∈ z^+$ then which of the following is true?
a) f is a bijective mapping
b) f is a injective but not surjective mapping
c) f is a not injective but surjective mapping
d) f is neither injective nor surjective