Which Statement About How Breathing Is Regulated Is True

Which statement about how breathing is regulated is true?

A) Mammals are quite sensitive to decreasing levels of O₂ in their arterial blood.
B) The brainstem posterior to the medulla regulates breathing.
C) Fishes are very sensitive to decreasing levels of O₂ in their arterial blood.
D) In mammals, a small increase in arterial PCO₂ prompts no change in ventilation.
E) Severing the spinal cord does not stop breathing in mammals.