In the lemon shark experiment, what is the control group?

• A. The tuna with lead
• B. The samarium
• C. The shark
• D. The water

Answer: (A)

The main idea is that a control group is the baseline that does not receive the experimental treatment, used for comparison to see the effect of the variable you’re testing. If the lemon shark experiment is looking at whether lead in prey affects the shark, the independent variable is lead exposure in the tuna. The control would be tuna that has not been exposed to lead, so any differences in the shark’s behavior can be attributed to the lead itself. The tuna with lead describes the group that actually gets the treatment, not the baseline. The other options don’t fit as a control because they don’t isolate the prey’s lead exposure: samarium is a different element, the shark is the subject, and the water is just the environment kept constant. In a proper setup, you’d compare sharks feeding on lead-free tuna to sharks feeding on lead-treated tuna to see the effect of lead.