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

a look at the data for the control group to see how much the fish grew without the new food.

b check the lab results to see if the researchers changed the dependent variable in the same way
.
c examine the data to find how the researchers changed the variables within the control group.

d determine if the results show the independent variable changing as the dependent variable was changed.

Answer is: A look at the data for the control group to see how much the fish grew without the new food.

The two main variables in an experiment are the independent and dependent variable.

Dependent variable (in this example the fish grew) is the variable being tested and measured in a scientific experiment.

Dependent variables depend on the values of independent variables (in this example the food). The dependent variables represent the output or outcome whose variation is being studied.

The correct answer is "look at the data for the control group to see how much the fish grew without the new food."

Looking at the control group is very important as fish in the control were not given this new food. So how well did the fish grow in the absence of the new food must be understood.

Here the growth of the fish is the dependent variable as its growth may or may not depend on the new food. The new food is the independent variable which is being tested to see its effect on the dependent variable.  

the answer is c i believe