Final answer:
In a study, the dependent variable is the weight gained.
Step-by-step explanation:
The dependent variable is the variable that is being measured or observed and is affected by the independent variable. In the given scenario:
a) The doughnuts: This is the independent variable, as it is the factor that is being manipulated or controlled.
b) The boys: This is not the dependent variable, as it remains constant throughout the study.
c) The duration of a week: This is also not the dependent variable, as it is a constant parameter.
d) The weight gained: This is the dependent variable, as it is being measured and affected by the consumption of doughnuts.