Documents of title to goods are legal documents that provide evidence of ownership or control over goods. They are important in commercial transactions as they allow the transfer of ownership or possession of goods from one party to another. Three common documents of title to goods are railway receipts, wharfinger's certificates, and warehouse keeper's certificates.

Railway Receipt:
- A railway receipt is a document issued by a railway company to the sender of goods as proof of receipt. It is generated when goods are handed over to the railway company for transportation.
- The railway receipt contains details such as the name and address of the consignor and consignee, description of the goods, weight, and the destination.
- It serves as evidence of the contract of carriage between the railway company and the consignor, and also acts as a negotiable instrument for the transfer of ownership or possession of the goods.

Wharfinger's Certificate:
- A wharfinger's certificate is a document issued by a wharfinger, who is the owner or operator of a wharf or dock, to acknowledge the receipt of goods for storage or shipment.
- It contains information such as the name and address of the consignor and consignee, description of the goods, quantity, and condition.
- Similar to a railway receipt, a wharfinger's certificate serves as evidence of the contract of storage or shipment and can be used for the transfer of ownership or possession of the goods.

Warehouse Keeper's Certificate:
- A warehouse keeper's certificate is a document issued by a warehouse keeper to the depositor of goods stored in a warehouse.
- It includes details such as the name and address of the depositor, description of the goods, quantity, and storage location within the warehouse.
- This document serves as evidence of the contract of storage between the warehouse keeper and the depositor, and can be used to transfer ownership or possession of the goods.

All of the above:
- The correct answer is option 'D' - all of the above. This is because all three documents - railway receipt, wharfinger's certificate, and warehouse keeper's certificate - are considered documents of title to goods.
- Each document provides evidence of ownership or control over goods and can be used for the transfer of ownership or possession in commercial transactions.
- These documents are widely recognized and accepted in trade and commerce, facilitating the smooth flow of goods and ensuring legal protection for the parties involved.