D. Marine bills of lading may be transferred and mortgaged.
Explanation: A bill of lading is a document issued by a carrier (usually a shipping line or freight forwarder) to acknowledge receipt of goods for shipment. It serves as a contract of carriage and a receipt for the goods. Option D is correct because marine bills of lading are indeed transferable to other parties, such as buyers or banks, as a form of security or payment for goods.