Correct Answer: D

Rationale: Cracks at the corners of the mouth, known as angular cheilitis, can be a sign of vitamin B deficiency, specifically B2 (riboflavin) or B3 (niacin). The nurse should ensure that the client receives adequate B vitamins through foods rich in these nutrients or supplements to address the deficiency, which can help improve the condition of the client's mouth.

Correct Answer: B

Rationale: Montelukast, a leukotriene receptor antagonist, is primarily prescribed to prevent asthma attacks. It works by reducing inflammation and bronchoconstriction in the airways, thereby helping to control asthma symptoms and prevent exacerbations.

Correct Answer: B

Rationale: Gingival hyperplasia, or overgrowth of the gums, is a common side effect of phenytoin. Patients should maintain good oral hygiene to minimize this effect.

Correct Answer: B

Rationale: Tiotropium is a long-acting bronchodilator used to relieve bronchospasm and improve airflow in patients with chronic obstructive pulmonary disease (COPD). It works by relaxing the muscles around the airways, leading to bronchodilation and improved breathing, making it an essential treatment in managing COPD symptoms.

Correct Answer: C

Rationale: The correct instruction for a patient prescribed metformin is to take the medication with meals. This helps reduce gastrointestinal side effects commonly associated with metformin. Patients should also be educated about the signs of lactic acidosis, a rare but serious side effect associated with metformin use.