Answer:
freight
Step-by-step explanation:
Given that FREIGHT is a term or register word that describes a form of goods being transported either over land or water from one place to another. It is usually smaller compared to cargo, but still a form of shipment.
Hence, in this case, the correct answer is " steamboats carry FREIGHT between towns"
Luggage is just a term for bags or suitcase carried along during traveling, hence, this is not correct
Content is a term for what is inside of something, hence, this is not correct.
Belonging is a term for man's possession or things that can easily be carried along. Hence, this is wrong as well.