Final answer:
The ethical principle applied when a client asks about her prognosis is Veracity, which involves being truthful with patients.
Step-by-step explanation:
The ethical principle used when a client asks about her prognosis is B. Veracity. This principle compels healthcare professionals to tell the truth and be honest with their patients. When a patient inquires about their prognosis, it means they are seeking information about the likely course and outcome of their medical condition. Upholding the principle of veracity means providing a truthful, yet compassionate, response to the patient's inquiry, even when the information may be difficult to hear. While nonmaleficence and beneficence are also important ethical principles in medicine, which avoid causing harm and promote the well-being of patients respectively, it is veracity that is directly concerned with honest communication.