how to set a selected value in $form->select function? need help

in my edit function, i need to reselect for the field again to save it.
how can i added a 'selected'=>$addresscountry field in my $form->select function??

this is my code..

Choose Your Country'

which $country is 1 of the helper that include by the page, let user to select country.
i need it automatic to refer back to the previous data which had save, means add a selected value in my edit function.

any 1 can help? thanks..