If you pass an array to the update_option it will automatically serialize it. you can later retrieve them back into an array like this.

$tempoptions = get_option("plugin-options");
if (!empty($tempoptions)) {
	foreach ($tempoptions as $key => $option)
		$options[$key] = $option;
}	

then do something like var_dump ($options) this will show you the entire array.

I think they use the maybe_serialize/maybe_unserialize/is_serialized functions from the codex, but I never really looked into it. Just found them now. 
http://codex.wordpress.org/Function_Reference/maybe_serialize