Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?

• A. One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all
• B. The lungs can be made fully empty by forcefully breathing out all air from them
• C. One can breathe out air totally without oxygen
• D. One can breathe out air through eustachian tubes by closing both the nose and the mouth