How does chlorine enter the oceans?
Volcanoes
Lungs.
Mars does have oxegyn actually, although it's really little because of the interaction between the CO2 in it's atmospere interacting with the sun. Btw people, please stop saying Mars has no oxegyn!
placer deposits
A gas tank
oxegyn in the air
No, there are no gases on the moon as there is no atmosphere.
Yes.
oxegyn and animals
Air Pollution Beer Oxegyn
Maybe but if it does it will be in very tiny amounts