Final answer:
The correct answer is diffusion of responsibility, where Sally and other bystanders fail to act in an emergency, assuming someone else will.
Step-by-step explanation:
In the scenario where Sally witnesses a man having a fit and doesn't take action because she assumes that someone else has, the lack of help from her and the other bystanders is the product of diffusion of responsibility. This social psychological phenomenon occurs when individuals in a group fail to act because they believe someone else will, thereby spreading the responsibility among the group instead of taking personal initiative. It is not related to social comparison, which involves looking to others to determine how to behave in ambiguous situations. Therefore, the correct answer to the question is: 1) only diffusion of responsibility.