Final answer:
The client's understanding of the teaching can be identified by their question about potential side effects.
Step-by-step explanation:
The nurse should identify statement 2) as an indication that the client understands the teaching. When the client asks the nurse about potential side effects of the medication, it shows that they are seeking information and demonstrating an understanding of the importance of being aware of the medication's potential effects.
Statements 1) and 3) are not accurate indications of understanding. Taking diltiazem with food is not necessary, as it can be taken with or without food. Requesting a refill of the prescription before it runs out does not necessarily indicate an understanding of the medication.
Statement 4) is actually concerning because stopping other blood pressure medication without consulting a healthcare provider can be dangerous.