Practice question

Correct option is B, 45 mm Hg. In Respiratory System; Exchange of Gases, the accurate description is 45 mm Hg, and that is what you should commit to memory. Keep the definition tight and the role clear — 45 mm Hg is the option that correctly names the structure, process, or principle asked for in Respiratory System; Exchange of Gases. Then 45 mm Hg is the answer you can defend. Check yourself by covering the options and writing the answer first, then matching the letter — that builds confidence. If the wording feels dense, translate it into everyday language first, then map that plain sentence back onto 45 mm Hg.