Epic Tuition Scene :P

During tuition yesterday, we had this question and answer session for Science. My question was this:

Which of the following gasses in the air in not harmful to the respiratory system?

A. Sulphur dioxide

B. Carbon monoxide

C. Nitrogen dioxide

D. Carbon dioxide

ME: The answer is C

SIR: You sure?

ME: Yes

SIR: You're wrong. Does that mean our lungs get damaged every single time cause respiration contains carbon dioxide?
ME: *speechless*

LOL paiseh lah xD But funny :P