The Kansas City, Missouri, Police Department's Study of Patrol Effectiveness

The Kansas City, Missouri, police department's study of patrol effectiveness convinced criminologists that:

A) The mere presence of patrol officers on the street did not have a deterrent effect.
B) Doubling the amount of patrol officers on the street had a deterrent effect.
C) The mere presence of patrol officers on the street had a deterrent effect, but only in high-crime neighborhoods.
D) Decreasing the amount of patrol officers on the street increased crime.