3/5/10 Animals exhale methane

Discover films have 700 options that sometimes do not fit.
This makes no remote sense whatsoever.

How many miles is 4 miles?
Um...4?

What do animals exhale? I think it's methane.
(the whole class says CO2)
*gives puzzled look*
*picks up worksheet*
"Oh, it's CO2. They exhale methane out of their butts."
Alright, this is seriously scary.