A vessel loads 5000 tons of manganese ore. The railroad cars that brought the ore to the vessel were previously loaded with iron ore so the ore is contaminated. The agent requests the Master to sign a Clean Bill of Lading and in return the shipper will give him a Letter of Indemnity. What is the best procedure to follow? （）

A.Sign a Clean Bill of Lading and accept the Letter of Indemnity
B.Refuse to sign a Clean Bill of Lading
C.Sign the Clean Bill of Lading and have the agent countersign it
D.Sign a Clean Bill of lading under protest