a.three or more people who have common goal get together to achieve the goal better

b. Interdependence 

The mutual dependence of group members on one another.

     Common goal

The driving force that brings people together to form is a common goal.

     Group personality 

  When people come together in a group, they form a collective identity that becomes the group personality.

      Commitment 

Commitment is the desire of group members to work together to complete their task to the satisfaction of the entire group.

       Cohesiveness 

Cohesiveness, an extension of commitment, is the attraction that group members feel for each other and their willingness to stick together.

        Group conflict 

The truth of the matter is that whenever people come together in any communicative context there is bound to be conflict of some sort.

     Social facilitation 

The tendency for a person to release energy that would not be released if the individual were acting alone is called social facilitation.

   Gender differences 

Research shows that groups consisting of both men and women are more likely to be dominated by men talking than by women talking.

  Group size

A group is composed of a number of people who are brought together or who come together voluntarily and who share a common goal, task, or purpose.

 Norm

Norms are the expected and shared ways in which group members behave.

c.

1.Clear objectives and what the members talk about should be related to the topic and goals

2.Relatedness. make sure that contributions tie in with what has been said before and what is apt to be said next.

3.introduce a good idea at a favorable time

4.when you make a comment,to make sure that the comment you contribute is long enough to make your point.

5.when you say something, show the ideas clearly to make other people understand what you say easily.

6.when you say something ,make sure that what we say are accurate. so we should make a full preparation and do prior research.