The Introduction to Chapter 2 Began with Descriptions of Disagreements

The introduction to Chapter 2 began with descriptions of disagreements over the relation between television violence and aggressive behaviour,and of situations in which people won't intervene to stop violence.Why would authors begin Chapter 2 by describing these phenomena?

A) There are competing explanations for both phenomena, and research methods can be used to establish the best explanation.
B) These topics address the most difficult issues that social psychologists will ever study.
C) Definitive explanations for both phenomena have been provided by social-psychological research.
D) These topics are a good example of what has yet to be studied in social psychology.
E) There is more literature on violence and aggression than on any other topic of interest to social psychologists.