Water, a stable liquid, is formed when two flammable gases, hydrogen and oxygen, combine. What has happened? O An atom has been created.
O A compound has been created,
O A mixture has been created,
An element has been created

A compound has been created

Explanation:

Remember you cannot create an atom nor can you create an element so An atom has been created and An element has been created is incorrect. Also, a compound is something that is chemically bound and cannot be separated unless applied a chemical change, which is applicable to water. It cannot be a mixture since mixtures can be separated physically, which you can't do with water.

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.