Question

read the following excerpt from levitt and dubners freakonomics.
a key fact of white - collar crime is that we hear about only the very slim fraction of people who are caught cheating. most embezzlers lead quiet and theoretically happy lives; employees who steal company property are rarely detected.
with street crime, meanwhile, that is not the case. a mugging or a burglary or a murder is usually tallied whether or not the criminal is caught. a street crime has a victim, who typically reports the crime to the police, who generate data, which in turn generate thousands of academic papers by criminologists, sociologists, and economists. but white - collar crime presents no obvious victim.
in this excerpt, the authors present
a comparison between various criminals.
an argument in favor of reporting crime.
a contrast between different types of crime.
an argument against embezzlement.

Explanation:

The text compares white - collar crime (where only a small fraction of cheaters are caught and there's no obvious victim) with street crime (where crimes are usually tallied as there's a victim who reports). This is a contrast between different types of crime.

Answer:

a contrast between different types of crime.