# Combining 2 problems in NP into one

Say I have a deterministic turing machine which solves decision problem S with oracle access to both problems B, C that are in $$NP$$. Can S be solved with oracle access to only one problem in $$NP$$?

That is, can B and C somehow be combined into one problem in $$NP$$ (thus showing S is in $$P^{NP}$$)?