Final answer:
The phrase 'closed shop' in the context of a healthcare facility means that a nurse must join a union to be employed there. This represents mandatory union membership as a condition for employment, an arrangement that can affect the labor market for nursing and other healthcare professionals.
Step-by-step explanation:
When a health care facility is referred to as a closed shop, it means that the nurse must join a union as a condition for employment. Therefore, the correct answer to what the phrase 'closed shop' means to the nurse is A. The nurse must join a union to be employed there. In such an arrangement, labor unions and employers have an agreement that the employer will only hire union members, and future employees must become union members before commencing work. This practice can directly influence the labor market for nursing and other healthcare professionals.
Such requirements are meant to ensure that all workers within the organization are members of the union, offering consistent terms and agreements for all employees. This type of mandatory union membership can also be found in other professions, where membership could be required to practice, as seen with the American Bar Association for lawyers.