【单选题】Which of the following statements about the harmful effects of hemoglobin bound with CO (COHb) is wrong?
A.
At levels of less than 10% of total hemoglobin, symptoms are rarely observed. At 15%, the individual experiences mild headaches.
B.
At 20% to 30%, the headache is severe and is generally accompanied by nausea, dizziness, confusion, disorientation, and some visual disturbances; these symptoms are not generally reversed if the individual is treated with oxygen.
C.
At COHb levels of 30% to 50%, the neurological symptoms become more severe, and at levels near 50%, the individual loses consciousness and can sink into coma. Respiratory failure may follow. With prolonged exposure, some damage becomes permanent.
D.
Death normally occurs when COHb levels rise above 60%.