Which of the following was identified as an enduring puzzle of the American criminal justice system?

a. the inability of police departments to recruit and hire a more diverse police force
b. the inability of police departments to use body-worn-cameras or other technology that can help increase transparency
c. the inability of police departments to properly train and discipline their officers to minimize the use of force
d. the inability of police departments to keep their community up-to-date on crime issues