Asingle business is a if it has achieved exclusive control over a product or service.

A single business is a monopoly if it has achieved exclusive control over a product or service.
For example, Microsoft is a monopoly, because it owns rights to all of its products and it doesn't share them with any other company.

The advantage of administering personality tests on employees is that it will allow the employer to know the mindset and personality of the employee. this will allow the employer to at least have an idea as to how the employee works and how his attitude in the workplace. the disadvantage is that it may make the employee a little anxious as to whether he would meet the personality requirements of the employer and whether he would be able to retain the job or not.