The best answer here is your fourth one, they only present facts regarding a topic. When writing for information, as the author you want to ensure your readers are being presented with correct information. To do this, you must research before placing your information into whatever it is you're writing. When you do this, you don't want to give your readers incorrect information. Thus, your writing must be based on provable facts.
The other three options are all things that are included in other types of writing as well as informative writing, which is why they are not the best answer here.