Final answer:
For a patient with hypomagnesemia receiving magnesium sulfate IV, the normalization of deep tendon reflexes to 2+ is an indication of therapeutic effectiveness of the treatment.
Step-by-step explanation:
The most appropriate finding that should indicate to the nurse that the medication is effective for a client who has hypomagnesemia and is receiving magnesium sulfate IV is b. 2+ deep tendon reflexes. Magnesium plays an important role in neuromuscular function, and profound magnesium deficiency can lead to decreased reflexes. Restoring magnesium levels should normalise deep tendon reflexes, typically measured on a scale from 0 to 4+, with 2+ indicating a normal response.