Step 1 :The question is asking for the dependent variable in the situation. In this case, the dependent variable is the outcome that is measured, it's the result of the independent variable. In this situation, the number of books Emmitt reads is the independent variable, and the dependent variable is the amount of extra credit Emmitt receives from his history teacher. This is because the amount of extra credit Emmitt receives depends on the number of books he reads.
Step 2 :Final Answer: \(\boxed{\text{The amount of extra credit Emmitt receives from his history teacher.}}\)