Answer:
a. Service occupations, Administrative Support, Professional Specialty
Step-by-step explanation:
About 63.1 percent of the United States population was eligible to work and participated in the job market as per 2019 data.
50 percent of the United States population is engaged in the civilian workforce. The civilian labor force involves workforce like service occupations, administrative support, professional specialty, and other civil occupations. Agricultural workers, military personnel, and federal government employees are not part of the civilian workforce.
Hence, the correct answer is "a. Service occupations, Administrative Support, Professional Specialty".