Explanation:

• Entrepot Ports: These are collection centres where the goods are brought from different countries for export. Singapore is an entrepot for Asia, Rotterdam for Europe, and Copenhagen for the Baltic region. Hence option (b) is the correct answer.
• Packet Station or ferry ports: These are exclusively concerned with the transportation of passengers and mail across water bodies covering short distances. These stations occur in pairs located in such a way that they face each other across the water body, e.g. Dover in England and Calais in France across the English Channel.
• Out Ports: These are deep water ports built away from the actual ports. These serve the parent ports by receiving those ships which are unable to approach them due to their large size. For example, Athens and its out port Piraeus in Greece.
• Ports of Call: These are the ports which originally developed as calling points on main sea routes where ships used to anchor for refuelling, watering and taking food items. Later on, they developed into commercial ports. For example: Aden, Honolulu and Singapore.