Need help to Create this simple plugin !

Hello !
I am trying to write a plugin for a social bookmark site.

here is part of the command:

$link_adb = "<a /><br />
h ref=\"http://www.livewire.com/api/add?url=".get_permalink()."&title=".get_the_title($id)."&tags=".get_the_category($cat)."\">".$text_adb."";

The link incooperate the permalink and title fine. but not the category. I am really not sure what command should i use to pull the category in which the post is made, or if i want to use a category say id 2.

I would really appreciate if someone can help me with the above command to fix the bug in category.

Regards
samantha