The correct option to this question is option 3. Doing or saying what others around us say or do; coming to feel or think as others do.
Basically, conformity is a broad term used to converge thoughts, feelings, and behaviors of individuals towards a group's norm. In public conformity, individuals are forced to conform to group norms rather than disagreeing group's point of view, doesn't matter group's norm is right or wrong. However, individuals think the group is wrong in a private manner. In the case of private conformity, people actually believe the group is right.
Psychology involves the study of the mind and behavior of people. Psychologists want to know why people do the things they do. Sometimes, people will do things because they feel that others expect them to do these things. Public conformity is when people act or speak what others say or do. They will mimic or copy their actions or words because they are conforming to society. Then they would fit into society.
For example, if people were in an elevator and turned to face away from the door, the next person who entered the elevator may do the same thing. Private acceptance is when someone will feel or think as other people in society do. In this case, these people take conformity a step further.