Final answer:
The control variable is the type of thermos brand being tested, the independent variable is the different thermos brands, and the dependent variable is the temperature of the water in each thermos brand.
Step-by-step explanation:
In this experiment, the control variable would be the type of thermos brand being tested. The control variable is kept constant throughout the experiment and is used as a point of comparison.
The independent variable would be the different thermos brands being tested, as these are the variables being manipulated. The dependent variable would be the temperature of the water.
In each thermos brand, as this is the variable that is being measured and will be compared.