Key shortcut to open drop-down list


I am completely new to all of this and looking around for help.I open new sheet, select A1 and then add some drop-down list by going through Data Validate settings.After selecting A1 the drop-down list open button appears on the right and I can click it and select a predefined value that would be then transfered to A1.I have question that how do we open the list and select the value using keyboard only?
Is it even possible to do that? I can’t find that information in the help system nor in google.I went through many resources but did not find any solution for this issues. Please help me out.

Any help will be appreciated.
Thank you.

You can expand the dropdown list with (left)Alt + down arrow