Refer to the Figure Showing Feedback Information That Controls Breathing

Refer to the figure showing feedback information that controls breathing in humans. The nerves labeled 1 are _______; the structure labeled 2 senses the _______; and the nerve labeled 3 is _______.

A) sensory; O₂ content of the blood; a sensory nerve that goes to the heart
B) sensory; hydrogen ions in the cerebrospinal fluid; a motor nerve that stimulates the diaphragm to contract
C) sensory; N₂ content of the blood; a motor nerve that innervates the intercostal muscles
D) motor; O₂ content of the blood; a sensory nerve to the diaphragm
E) motor; pH of the blood; the phrenic nerve