Because you wouldnt want to state that something is a fact when it is really not.
Answer:
The narrator which is one of the kids describes their family living in a town with a rich man and his kids living in a big house besides them. The narrators family often goes out to play and have fun while the rich kids stayed inside the house and kept the windows closed.
Explanation:
Hope this helps!
The only sentence which is not a proposition is Sit down, because this is imperative, you are ordering somebody to do something, whereas propositions merely inform.
