Choice A rationale:

The nurse should obtain post-transfusion laboratory tests immediately after the transfusion to assess the patient's response to the blood transfusion.

These tests may include a complete blood count (CBC) to evaluate hemoglobin and hematocrit levels.

Choice B rationale:

Returning any unused blood product to the blood bank is not the immediate action needed after a transfusion.

Post-transfusion laboratory tests and patient assessment take precedence.

Choice C rationale:

Removing the IV catheter without flushing it immediately after the transfusion is not appropriate.

The IV site should be maintained for a period after the transfusion to ensure there are no adverse reactions, and the catheter should be flushed according to the facility's protocol.

Choice D rationale:

Educating the patient about the procedure is important but should be done before the transfusion, not immediately after.

Immediate post-transfusion care involves monitoring the patient and obtaining necessary laboratory tests.