Answer:
given in explanation.
Step-by-step explanation:
Independent variable is one which is controlled or changed by the scientist.
In this question the variable statement is
Watering the plant with different concentration of salt. Concentration of salt is controlled by the Marty so it is independent.
Dependent variable is one which is being tested or measured in an scientific experiment.
Marty measuring the sunflower height after the experiment is dependent variable.