How can I use one field to filter the drop-down options in another field?

Thank you @shantanukumar847 This certainly got me a lot further than when I started. In the example provided, they are performing a search. I need to SAVE the selected data to the database collection because my fields are on a registration form. I needed to narrow the choices when someone is registering so that when they submit it saves to the database collection for future reference. Any suggestions?