Decision problem which belongs to P reduced to a decision problem which belongs to NP? Is it possible to have a decision problem $A$ which belongs to P and reduce it to a decision problem $B$ which belongs to NP, i.e. $A \leq_{\mathrm{p}} B$, where $A$ belongs to P, $B$ belongs to NP?
Of course. Just take B=A, since every P problem is in NP.