I'm not sure but I think non of them! I think it's better to rewrite this sentence as below: "Those are the table legs" We're speaking about ST which is known for us and we have to use "the" before the table, About the table and table's or legs of the table I don't really have an idea but I think we can use "table legs" here!

Hi Lorena! All of them are reasonable. Each sentence has a different feeling to me, and fits a different situation. Let's try to imagine a story that matches each sentence. 1. Those are the table's legs. 2. Those are table's legs. 3. Those are the legs of the table 1. I have only one table. I needed to put my apartment possessions into storage so the table was taken apart. Hmm, here is the table top. There are many boxes of books and stuff, and -- oh look! There are the table's legs! 2. My uncle works in a carpenter's shop. They make all kinds of furniture there: cabinets, bookcases, tables and chairs -- everything! Here is a pile of boards ready to be made into something. Those are drawers for a dresser. Those are table's legs. 3. This is just like 1. but maybe we can imagine another case. There was a storm and a flood and my house was mostly destroyed. The books are floating in the water. Many pieces of furniture have been smashed into bits. This is the cover of a trunk. That is the shelf from a bookcase. These cushions are what is left of the sofa. Those are the legs of the table. I hope this helps :)