The following experiment is conducted to study the causes of aggression in children. Half the children eat a sugared cereal; the remaining half eats cornflakes. The number of aggressive acts displayed by the children in a one-hour play period after breakfast is then recorded. In this experiment:_______.
a. sugared cereal is the dependent variable and corn flakes is the independent variable.
b. breakfast is the independent variable, and the group of children is the dependent variable.
c. the type of cereal is the dependent variable, and the number of aggressive responses is the independent variable.
d. the type of cereal is the independent variable, and the number of aggressive responses is the dependent variable.

The experimental research method is a research methodology in which the independent variable is manipulated to examine its impact on the specific dependent variable.

In the given example, the 'type of cereal exemplify the independent variable while the number of aggressive responses would be the dependent variable' as the independent variable('type of cereals like sugared cereal, cornflakes') is manipulated to observe its significance or effect on the 'aggressive responses' by the children which is the dependent variable(directly dependent on the independent variable). Therefore, option D is the correct answer.