27. The Kjeldahl digestion is a method for the quantitative determination of nitrogen contained in organic samples. Firstly the sample is oxidized by concentrated sulfuric acid at high temperature, and then the N-containing products are separated from other products and quantized. Which of the following sets of substances are produced in the oxidation reaction? (A) CO2, H2O, N2 (B) CO2, H2O, (C) C, H2O, HNO3 (D) CxHy, H2O, CO2, HNO3 (E) CxHy, H2O, CO2, HCN