How to display the selected value from the drop-down box?
form_test_form_submit is called in php that's not displayed to user. Form is processed, it's values saved, and user is taken to desired page. Now you have 2 options:


In submit handler set$form_state['redirect'] to a page you like. Save values to a database. On target page read them and display.
In validation handler add markup elements with selected values, if you want to emphasize selection but leave user on a form.