What are the two gases that animals exchange and their surroundings
a. oxygen and nitrogen
b. nitrogen in helium
c. hydrogen and carbon dioxide
d. corbin the outside and oxygen

The double bond between a carbon atom and two oxygen atoms (a molecule of carbon dioxide) has two characteristics. what are they? a.an ionic bond is formed between the oxygen and carbon atoms. b.four valence electrons are shared. c.two valence electrons are shared. d.valence electrons are shared between oxygen atoms.

Due tonight 10 points will mark brain

Why do mountaineers become breathless as they reach high altitudes