Answer:
In this study, the amount they eat for dinner is the dependent vairable and the no nap group is the control group.
Step-by-step explanation:
In the studies there are independent and dependent variables, in which the first ones, determine the second ones, this means that you control the independent variables establishing in this case the time each group is going to nap, and analize the effects of this with the dependent variables, in this case you are going to record the amount they eat for dinner, because you want to establish the relationship between daytime toddler naps and dinnertime appetite.
So
Control - Independent (control naps time)
Results - Dependent (amount they eat)
Now, the control group is the one that doesn't takes a nap, because you need a referent point so you can compare the different scenarios.