What is the best mapping option for a page button element located within an iFrame source?

Set up a new activity rule based on the clicked element from the iFrame and ask the webmaster to place the Tag Manager code within the iFrame source
Set up a new activity rule based on the URL of the page containing the button
Ask the webmaster for the button’s CSS selector and set up a new activity rule based on the clicked element
It is not possible to map a button on a page