Please help I’ve been stuck in this question and am completely lost

Which experiment would most likely contain experimental bias

Consider the following planned experiment. factor experimental group control group light exposure tots of sun tots of sun amount of water weekly weekly type of soil nutrient rich nutrient rich size of pot large which variable is being tested in this experiment? small a. size of pot b. type of soil c. light exposure d. amount of water

Tom wants to conduct a scientific study but he needs to finish by the end of the school year. what practical way could tom work around this limitation and be successful in his study?