Final answer:
A nurse should allow the elderly client to express emotions and share memories, as this supports emotional well-being and aids in the grieving process.
Step-by-step explanation:
The correct action a nurse should take when caring for an older adult client who is expressing feelings of grief and longing for his earlier life is to allow the client to share memories and express emotions. Option d) is the most therapeutic approach as it helps in validating the client's feelings and facilitates the grieving process, which is a natural response to loss. Providing a supportive environment for reminiscence can help the elderly person feel valued and understood, ultimately contributing to their psychosocial well-being and aiding in their adjustment to changes associated with aging.