Final answer:
If the nurse discovers that the patient has no usable veins in either arm, they should contact the physician and report the concern.
Step-by-step explanation:
If the nurse discovers that the patient has no usable veins in either arm, the appropriate course of action would be to contact the physician and report the concern (D). This is because the nurse should inform the physician of the problem and seek guidance on how to proceed. The physician can provide further instructions or make alternative arrangements for the patient's IV line.