The correct answer is D. If there are fewer bystanders, someone is more likely to help the victim.
Step-by-step explanation:
The Bystander Apathy is a psychological phenomenon in which bystanders or observers are less likely to help if there are other people around, this occurs because individuals do not feel responsible for helping or expect someone else to take the lead. Despite this, the bystander effect is reduced if there are fewer bystanders because in this case, it is more likely someone feels responsible and decides to help.
According to this, in the case presented the factor that would increase the chances of the victim to receive help is "if there are fewer bystanders, someone is more likely to help the victim" because according to this phenomenon the more bystanders there are the less likely it is someone helps.