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.