Correct Answer: B

Rationale: After administering nitroglycerin, the next priority action is to monitor the client's blood pressure. Nitroglycerin can cause vasodilation and subsequent hypotension, so it is crucial to assess the client's blood pressure to prevent complications and ensure safety.

Correct Answer: D

Rationale: Rotating the application site every 24 hours is essential to prevent skin irritation and ensure consistent absorption of the medication. This practice helps to maintain the effectiveness of the nitroglycerin patch and reduce the risk of local skin reactions.

Correct Answer: C

Rationale: Nausea is an early sign of theophylline toxicity. The nurse should closely monitor the client for this symptom as it can progress to more severe toxicity. Nausea can be a warning sign to prevent further complications and adjust the dosage as necessary.

Correct Answer: B

Rationale: Bradycardia is a common sign of digoxin toxicity. Digoxin can cause disturbances in the heart's electrical conduction system, leading to a slower heart rate. Therefore, the nurse should closely monitor the client's heart rate for signs of bradycardia, which could indicate digoxin toxicity.

Correct Answer: A

Rationale: Shortness of breath and frothy sputum are indicative of pulmonary edema, a serious condition that requires immediate intervention to improve oxygenation. Administering oxygen is the priority action to support the client's respiratory function and prevent further deterioration. Oxygen therapy helps increase the oxygen levels in the blood, alleviate respiratory distress, and support vital organ function. Prompt intervention with oxygen can help stabilize the client while further assessments and treatments are initiated.