@Lorna170
Answerring the question is all you have to do when it comes to "trivial" questions.
If it is more serious and you like to invite the guest to book, you can pre-approve (or do some more communication first). Not responding guests on inquiries better ignore instead of decline (BTW if it is a request you must accept or decline).
In former days it was possible to remove "pending" inquiries from the dashboard, but since the new layout we have to wait until they disappear (they will).