What is it called when when animals release water vapor into the atmosphere

Identify the electromagnets with poles that are reversed from the electromagnet shown above

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?

Acontrol during an experiment. might change remains constant does not exist does change