The use of oil of peppermint has been shown in some studies to have an antispasmodic effect on the smooth muscles of the urethra, potentially relaxing the external sphincter and promoting spontaneous urination. The aromatic compounds can also stimulate the parasympathetic nervous system. However, its efficacy is not universally guaranteed. Choice B rationale Inserting a sterile catheter is the most invasive but a highly effective last resort intervention when a woman is unable to urinate spontaneously and has a full bladder post-delivery. A full bladder can displace the uterus and prevent proper uterine contractions, increasing the risk of postpartum hemorrhage. Catheterization is a direct method to relieve bladder distension and its associated complications. Choice C rationale Analgesics are primarily used for pain relief and do not directly address the mechanical or neurological issues causing urinary retention. While pain can contribute to difficulty urinating, prescribing analgesics is an indirect approach and is not the most effective or immediate solution for an over-filled bladder causing uterine atony. Choice D rationale Pouring water over the perineum can be an effective non-invasive technique to stimulate the micturition reflex. The sensation of the water on the external genitalia triggers a parasympathetic response, which can lead to relaxation of the urethral sphincter and promote the urge to void. This is a common nursing intervention used before more invasive measures.