you cant
Yes, cabbage do have seeds. These seeds are the ones you plant to grow cabbage.
any plant that contains seeds is a fruit. like a tomato for example it is a fruit. watermelon does in fact contain seeds therefore it is a fruit. if you get a seedless watermelon you will notice white things on the inside where seeds would form. those watermelons were not fully grown thus do not contain seeds. so to answer your question watermelon is a fruit.
the seeds of a watermelon are all over
Watermelon seeds come from watermelons.
A cabbage is grown in a garden or a farm field. I see cabbage grown here in Wisconsin in both places.
If one lets a cabbage grow for long enough it will grow to seed as happens with many vegetables that are grown and used before they grow to seed. below is a link to one of many sellers of cabbage seed
An example if a fruit with two seeds is the watermelon. The watermelon has both white seeds and black seeds, which is the seed used to plant watermelon.
animals eat the watermelon and the seeds come out the digestive tract of that animal
All kinds of watermelon seeds are safe to eat.
cabbage seeds
As with all fruit seeds, watermelon uses animals to disperse seeds. When an animal eats a watermelon, the seeds generally pass through the digestive system unharmed. When the animal defecates, the seeds then come out (and embedded in the natural fertilizer).
Watermelon plants are easily grown from seed.