Vestigial structures. These are structural elements that once served a purpose but as the organism evolved now serves no purpose.
What do you mean? that is not can be answered
Answer:
B. Is what the scientists manipulate in the experiment.
Explanation:
The Independent variable is not dependent, or doesn't rely, on another variable in the experiment. So, it would make the most sense that they would manipulate the Independent so that they can watch and see how the dependent variable reacts to the manipulation, or the change, in the independent variable.