Answer:
Their duties are related, and their knowledge overlaps.
Explanation:
The Department of Labor of the United States, is the department that administers occupational safety, salary, working hours, etc. The department oversees the welfare of those who earn wages, seeking jobs, or retired people.
The Department of Labor grouped together the three separate occupations of plumbering, pipefitting, and steamfitting because their duties are somewhat related, and skills and knowledge intersect with each other.
<u>The duties performed by plumbers, pipefitters, and steamfitters include installing of pipes, fixing pipes, inspection of pipelines and pipe systems, repairment of pipes, etc. And the knowledge of pipe of all three occupations is also similar. It includes pipe system design, safety, tool use, etc.</u>
Thus the Department grouped them together because they have overlapping skills and knowledge, and similar duties. Therefore, the correct answer is the last option (D).
