- Fruit contains seeds
- If something contains something else then that something is a source of that something else
- So, fruit is a source of seeds

- Fruit is a source of seeds
- Fruit is a part of a tree
- So, fruit is a part of a tree that is a source of seeds

- Fruit is a part of a tree that is a source of seeds
- An oak is a kind of tree
- Therefore, fruit is a part of an oak that is a source of seeds

- Fruit is a part of an oak that is a source of seeds
- If something comes from something else then that something else is a source of that something
- Hence, fruit is a part of an oak where seeds come from

So, fruit is a part of an oak where seeds come from
The seeds of an oak come from the ___.
- Fruit contains seeds 
- If something contains something else then that something is a source of that something else 
- Fruit is a part of a tree 
- If something comes from something else then that something else is a source of that something 
- An oak is a kind of tree