Final answer:
A resting heart rate below 60 bpm is a reason to withhold the digoxin dose.
Step-by-step explanation:
A resting heart rate below 60 beats per minute is considered bradycardia. In the case of administering digoxin, a medication used to treat certain heart conditions, a heart rate below 60 bpm is a reason to withhold the dose and notify the healthcare provider. This is because digoxin can cause bradycardia as a side effect. Therefore, option d) is the correct answer - a reason to withhold the digoxin dose.