26 A 75-year-old man who lives alone in a poorly ventilated house without central heating uses a portable unventedkerosene heater to warm the house during the winter months. One morning, a neighbor finds him in an obtunded state. On physical examination, he appears cyanotic. Results of blood gas measurement on room air are Po2, 90 mm Hg; Pco2, 35 mm Hg; and pH, 7.3. Pulse oximetry shows low oxygen saturation. Exposure to which of the following is most likely to have produced this man's illness? (A) Beryllium (B) Carbon monoxide (C) Nitrous oxide compounds (D) Oxygen (E) Ozone (F) Polycyclic aromatic hydrocarbons (G) Sulfur dioxide