Final answer:
The priority nursing action for nonreassuring or ominous signs is to stop the medication Oxytocin.
Step-by-step explanation:
The priority nursing action for nonreassuring or ominous signs is to stop the medication Oxytocin (b). Oxytocin is commonly used to induce or augment labor, but it can have adverse effects on fetal well-being if there are signs of distress. Stopping Oxytocin allows healthcare providers to assess the situation and determine the appropriate course of action.