Final answer:
The most effective strategy to overcome diffusion of responsibility is to single out a specific person to take action, as it assigns clear personal responsibility.
Step-by-step explanation:
The question asks which strategy is most effective in overcoming diffusion of responsibility, a phenomenon where individuals in a group are less likely to take action because they believe someone else will do so. In situations like these, clearly and directly addressing a specific person to take action is the most effective way of counteracting this effect, making option 4 ("Singling out a specific person") the best choice. When you single out a specific person, you make it clear that the responsibility to act falls on them, thereby eliminating ambiguity and potential inaction that comes with diffusion of responsibility.
For instance, rather than just yelling 'Someone call 911!', you should point directly to a person and say, 'You in the blue jacket, call 911!' This direct appeal increases the likelihood that the person will feel personally responsible and take the necessary action.