Final answer:
The best response by the nurse is to acknowledge and validate the mother's grief and loss.
Step-by-step explanation:
The best response by the nurse in this situation would be option D: It must be hard to deal with such a precious loss. This response acknowledges and validates the mother's grief, showing empathy and understanding. Option A and option B do not address the mother's feelings and instead focus on other aspects. Option C may be comforting to some individuals, but it does not directly address the mother's emotions.