Final answer:
The healthcare sector holds the greatest global employment opportunity due to the aging population, but computer and information services also show significant job market growth in the United States.
Step-by-step explanation:
The greatest global employment opportunity among the options provided is in the healthcare sector. This industry is experiencing growth across various occupations, from entry-level positions like nurse's aides to management roles in the elder care system. This expansion is driven by the aging baby boomer population who are living longer than previous generations, creating a demand for healthcare services. Another area of significant job demand in the United States is the computer and information services sector, which includes roles like software developers. These positions typically require significant education and training. By contrast, sectors such as tourism also employ a vast number of people globally and are essential for locations that rely on the scenic and recreational value to attract visitors and their expenditures. However, based on the U.S. Bureau of Labor Statistics, healthcare, and computer services are showing notable growth in the job market.