Given a function $f:R_* \rightarrow R_*$ defined by $f(x)=\frac{1}{x}$, where $R_*$ is the set of all non-zero real numbers. Which of the following is true?

Question

A) $f$ is one-one only

B) $f$ is onto only

C) $f$ is many-one and onto

D) $f$ is one-one and onto