1. If you check out before leaving for the airport, the hotel will keep your bags for you.

I wonder why the hotel will keep the bags. Please advise.

I think this means that the hotel will keep (secure, take care of) the bags until the owner of the bags is ready to go to the airport.

Maybe a hotel guest needs to check out by 11:00 AM, but doesn't need to leave for the airport until 2:00 PM.  People at the hotel will take care of (safeguard) the bags until around 2:00 (or whenever their owner wants them back). It is easier for the guest not to have to be responsible for heavy bags.

2. Most of us in this office _______ lunch at noon.

A) make
B) have
C) bring
D) go

Answer B is correct. I wonder if C) is okay too.

I see why you are asking, but I wouldn't choose this answer.  People who bring their lunch probably bring it when they come to work, rather than at noon. In my opinion, B is a much better answer.