@Kathy6 -- there are two types of contacts you will get from guests -- (1) Inquiries (2) reservation requests. For an inquiry, you don't actually have to preapprove or decline, you just need to respond with some type of message within 24 hrs. You may wish to decline someone to make the matter more clear, but you are not obligated to do so. For a reservation request, you must accept or decline within 24 hrs. YOu can tell which is which because if you have the option to preapprove, you have an inquiry, not a reservation request. If you have the option to accept, you have a reservation request, not an inquiry. Also the email you get will state "inquiry" or "reservation request."
You can ask the guest to close an inquiry or cancel a reservation request. Sometimes they will do that and sometimes they won't, but if you would like the guest to do that, no harm in asking. Just dont' depend on them to do it and remember your 24 hr deadlines.
If you are getting too many inquiries or reservation requests from types of guests who dont' fit what you offer, you might try being more clear in your listing description about what you do offer and what you don't, to avoid getting too many respondents whom you end up declining, as a large number of declines will negatively effect where your property shows up in the search ranking (eg, you will be further back in search results if you do a large number of declines).