Research on bystander intervention, particularly the bystander effect, suggests that the presence of more bystanders can decrease the likelihood of offering help. This phenomenon occurs because people often look to others in ambiguous situations to determine whether help is needed. If others are not responding, they may assume that help is not necessary or that someone else will take action.
Therefore, based on the information provided, the option that suggests the highest likelihood of offering help is A) when there is only one other eyewitness. In this case, with fewer bystanders, the sense of responsibility and urgency to assist the injured pedestrian may be higher.