Final answer:
The physical risk to the participants is the ethical concern that an ethical review board would most likely be concerned about in this experiment.
Step-by-step explanation:
The ethical concern that an ethical review board would most likely be concerned about in this experiment is the physical risk to the participants. Having participants receive tattoos on their arms involves a physical procedure that carries potential risks, such as infection or allergic reactions. The size and color of the tattoo (option A), various perceptions of tattoos (option B), and the monetary cost of the tattoo (option D) are not significant ethical concerns in comparison to the potential physical risks to the participants.