Final answer:
The client statement that demonstrates understanding is to avoid taking antacids while on famotidine.
Step-by-step explanation:
The correct answer is B) I will avoid taking antacids while on this medication.
When a client is taking famotidine for peptic ulcer disease, it is important to avoid taking antacids as it can interfere with the medication's effectiveness. Antacids work by neutralizing stomach acid, whereas famotidine works by reducing the amount of acid produced in the stomach. By taking antacids, the client may counteract the effects of famotidine and reduce its efficacy in treating the peptic ulcer disease.