Carbon monoxide, a substance found in tobacco smoke, is also found in?

It is found in combustion fumes (by cars and trucks), portable generators, wood burning stoves, gas ranges and heating systems.
Hope this helps and have a great day!  :D

I’m going to guess these are the choices: a) recreational skiing developed in the mid-19th century b) it was originally invented as a way of getting from place to place in snowy regions c) downhill skiing is currently the only common form of the sport d) it mostly evolved from snowshoeing- if that’s the cases then the answer would be c) downhill skiing is currently the only common form of the sport