The question is? It is not a question if it has no interrogatory punctuation. I agree that "den" is good.
What do you mean by the -n form? nosotros? "let's?
"They give a lot of attention to the guests." is a STATEMENT, not a command.
When the instructions say "el mandato formal" do they m ean singular or plural? If there is no model, the answer might be "Dé" as these instructions are too OPEN and not SPECIFIC ENOUGH.
You definitely do NOT want estar, ir or ser.
What textbook do you have? I have never seen a textbook without a model (and I've seen some 30 years of textbooks!)
I have a textbook that has been nothing if not frustrating. Our homework is done online, and I have found mistakes in it (and I'm new at this). It is a first edition and the company refuses to fix the errors until its next edition. The text is called: Experience Spanish- Un Mundo sin Límetes Vol. 1, and it is published by McGraw-Hill. When I ask my teacher about some of these questions, she gives a suggestion and then shrugs her shoulders. Since the computer automatically grades some of the parts, I try to do my best to correct my errors, but sometimes, as you are seeing in the case of this problem, I can do nothing. Thank you so much for trying to help me. :-)
Thank you for telling me about your textbook. I am familiar with the older McGraw-Hill textbooks and they were good. There is NO perfect textbook, so you work with what you have. Knowing the title of your book, I can now go onlineto get more information. The more you tell me about your book, course, etc. the more I can help you! BTW, it is spelled "Límites" and I'm sure the Publisher still has help sites online. They used to and I'll let you know if and when I find something to help you.