Which of the following characteristics of today's police was taken up by municipal police officers after the American Civil War? A. They began to wear uniforms. B. They began to form posses. C. They began to carry out motorized patrols. D. They began to rely on police radios to aid police function.

In the Antebellum period, most states did not have an organized, municipally managed police force to maintain the peace. Most cities instead employed volunteer guardsmen or elected local constables, who would earn a salary by collecting the bounties that state judiciaries offered for wanted criminals and through a local fund that was specifically set up for the purpose of paying town sheriffs. However, the Civil War saw some of the most egregious cases of looting, public vandalism, theft, assault, and other petty crimes, in addition to more serious offenses such as sabotage and murder, in the country’s roughly eighty-five-year history. Thus, upon the conclusion of the War in 1865, major cities across the United States decided to establish a standing police force which would be maintained through public taxes. In order to standardize the police, navy blue uniforms were produced and distributed nationwide so that police officers would be easily recognizable anywhere in the country. The creation of the standard police uniform was the first step to the complete professionalization of the police in the United States.
Thus, the answer is A.
http://www.laphs.org/docs/blue-in-history-section.pdf