Answer:
The correct option is A) cadmium dosage
Step-by-step explanation:
In an experiment, an independent variable can be described as a factor which is changed naturally or by us to see its effect on the dependent variable. The dependent variable is the variable which is under study and depends on the independent variable.
In the following experiment, we are checking the effect of different dosages of cadmium on the surviving ability of tadpoles. Hence, cadmium dosage is the independent variable. Tadpole population is the dependent variable.