What is global warming? a) a recent increase in the average global temperature near earth’s surface b) a period of time when temperatures across the planet are colder than normal c) a characteristic of summer that returns seasonally d) the gain of heat in coastal areas from el niño storms

Global Warming is a gradual increase in the overall temperature of the earth's atmosphere.

So, i believe the answer to your question would be a) a recent increase in the average global temperatures near Earth's surface

Hydrogen = element

Carbon dioxide = compound

Water = compound

Zinc = element

Nitrogen = element

Salt = compound

Helium = element

Carbon monoxide = compound

Explanation:

An element and a compound are different when it comes to the types of atoms they possess. An element has only one type of atom while a compound has two types of atoms. For example, Hydrogen is an element because it has two atoms of the same type and that is, the "Hydrogen atom."

On the contrary, Carbon dioxide has one carbon atom and two atoms for Oxygen. Therefore, it is a compound because it has two types of atoms: Carbon atom and Oxygen atom.

Water has two atoms of Hydrogen and one atom of Oxygen. Therefore, it is a compound because it has two types of atoms: Hydrogen atom and Oxygen atom.