The correct answer is C. A direct relationship
Step-by-step explanation:
In science, a variable refers to a factor or quantity that changes usually because of other variables. Additionally, two or more variables can relate in different ways, for example, if one variable increases when the other decreases there is an inverse or indirect relationship. In the same way, when the variables studied increase or decrease together there is a direct relationship. For example, illness and death rate are directly related because as illnesses increase in a population the death rate also does. According to this, the type of relationship that occurs when two variables both increase or decrease together is a direct relationship.