Final answer:
The concept of deindividuation is best exemplified by how individuals in a group might engage in behavior, such as robbery, that they normally would not if acting alone, due to the anonymity and reduced sense of personal responsibility in a group.
Step-by-step explanation:
Deindividuation refers to a group situation in which a person may feel a sense of anonymity and a resulting reduction in accountability and sense of self. This psychological state can lead to behavior that is uncharacteristic for the individual, potentially including acts that are impulsive, deviant, or even criminal.
Among the options provided, option (b) a group of five individuals is more likely to perform an act of robbery than a single individual correctly represents deindividuation because it illustrates how individuals in a group might act in ways they might not alone due to the anonymity and reduced accountability of the group setting.