Final answer:
Informal groups address psychological needs and are governed by unspoken norms. These groups often include reference groups that influence individual behavior and typically have informal leadership without explicitly defined roles.
Step-by-step explanation:
Informal groups form to address the social and psychological needs of people. Informal groups are governed by unspoken norms and values. So the blanks in the student's question should be filled with 'b) psychological' for the first blank and 'iii) unspoken' for the second blank.
Reference groups are those whose values, norms, and beliefs come to serve as a standard for one's own behavior. Informal groups such as a circle of friends or a hobby group can serve as reference groups, influencing how individuals perceive themselves and how they behave.
Informal group leadership tends to be informal and emerge naturally within the group without explicit roles and responsibilities. These groups contrast with formal organizations, which have established structures and formal norms that guide member behavior.