<span>a. a substance that is naturally found in the brain</span>
Answer:
An event can cause changes to occur in one or more of the spheres, and/or an event can be the effect of changes in one or more of Earth's four spheres. This two-way cause and effect relationship between an event and a sphere is called an interaction. Interactions also occur among the spheres.
C. Common Ancestors are the animals that we evolved from
