Step 1: Locate each waterway's outlet sea.
Great Lakes to St. Lawrence to Atlantic Ocean. Volga to Caspian Sea. Danube to Black Sea. Mississippi to Gulf of Mexico.
Step 2: Match to the question.
Only the Mississippi's mouth sits on the Gulf of Mexico, at the delta south of New Orleans.
Final Answer:
Option (d) Mississippi waterways is correct.$\boxed{\text{Mississippi waterways}}$