The only personal experience most people have with the criminal justice process is contact with a: A. local police officer. B. courtroom. C. probation or parole officer. D. correctional institution.

You can find the answer to this question in chapter 6 of Robert Bohm and Keith Haley's Introduction to Criminal Justice. In this chapter, Bohm and Keith state that contact with a local police officer is the only experience that most people have with the criminal justice process. They also state that most people have never set foot in a courthouse or a jail.
In the same chapter, it is noted that administrators call the patrols carried out by local police officers "the backbone of the department." Patrols by local police officers are also described as the most time-consuming and resource-intensive task that officers undertake.
The duties of a local police officer on patrol include responding to burglar alarms, domestic disputes, and traffic accidents, as well as coming to the aid of people who have been hurt or injured. There are two types of patrol which local police officers might undertake. The first is known as random preventative patrol, and the second is known as directed, or guided, patrol. Directed patrol is determined by maps which indicate which areas of the community might need a patrol more than others.

There are two probable correct answers to this question, but any of them could be correct because the statement is vague in not defining who “most people” are. The two possible answers are A and B. In the United States, there are extreme demographic differences based on race, class, ethnicity, national origin, citizenship, and place of residence that affect contact with the criminal justice system. The majority of the US population is European-heritage, white, lower middle class, and urban. In many cities, police regularly patrol only poor and/or high-crime areas, so most people are likely to be put in infrequent contact with police officers. Adults are probably equally likely to enter courtrooms, even those who are not defendants or witnesses in a case. In the United States, jury duty is required of all citizens, but the time between required periods of service varies highly by jurisdiction and type of court, and some people may be excused from service.
https://www.sentencingproject.org/publications/un-report-on-racial-disparities/