An advertisement for a new fish food claims that lab studies show that fish grew three inches in three weeks while eating the food. Travis wondered if the food was worth the extra cost. To evaluate the claim in the advertisement, Travis should

look at the data for the control group to see how much the fish grew without the new food.
check the lab results to see if the researchers changed the dependent variable in the same way.
examine the data to find how the researchers changed the variables within the control group.
determine if the results show the independent variable changing as the dependent variable was changed.