Final answer:
The Safety needs of Maslow's hierarchy are most threatened when a new graduate nurse begins working, as they adapt to the healthcare environment and ensure their sense of security and protection.
Step-by-step explanation:
When a new graduate nurse begins working, the level of Maslow's hierarchy of needs that is most threatened is B. Safety needs. The safety needs on Maslow's hierarchy refer to the need for security and protection from physical and emotional harm, which is often a concern for fresh graduates facing the responsibilities of the healthcare environment. This stage follows physiological needs and precedes the need for love and belonging, the desire for esteem, and ultimately self-actualization at the top of the hierarchy, where an individual reaches their full potential. Considering the high-stress environment and the significant responsibility for patient care, it's understandable that safety needs would be a priority for new nurses as they acclimate to their new role.