If $f:R\rightarrow R$ is defined as $f(x)=[x]^2+[x+1]-3$ where $[x]$ is greatest integer of $x$, then what type of function is $f$?

Question

$\begin{array}{1 1} \text{many to one and onto function.} \\ \text{many to one and into function.} \\\text{one to one and into function.} \\\text{ bijection.} \end{array}$