Just preceeding line 29 of that file
defined('MOODLE_INTERNAL') || die();
Line 29: require_once($CFG->dirroot . '/mod/choice/backup/moodle2/backup_choice_stepslib.php');
Line 30: require_once($CFG->dirroot . '/mod/choice/backup/moodle2/backup_choice_settingslib.php');
comment after those lines:
* Provides the steps to perform one complete backup of the Choice instance
Do the backup_choice_stepslib.php and backup_choice_settingslib.php files reside in:
/[yourmoodle]/mod/choice/backup/moodle2
Looks like you are remotely hosted and may have FTP'd the extracted moodle version locally then uploaded. Some remotely hosted sites or FTP software may have issues with transferring a large number of files all at once. Are the files there? or are they missing? or do they have correct permissions for your system such that apache user can see them?
'spirit of sharing', Ken