Receive error message for radio buttons ."An illegal choice has been detected. Please contact the site administrator." I have created a multi step form, in which I have added radio buttons dynamically by using data from the database. The radio buttons added here are not required. But still I get the following error. I have created a custom module. 


  An illegal choice has been detected. Please contact the site
  administrator.


Kindly help me resolve this issue. This is not a duplicate issue. Other issues listed have mentioned that the radios button are used as required field in that case.
Please find the code added : 

$opt = array(
        'f' =&gt; 'Friend or Business Associate',
        'b' =&gt; 'Brochure',
        'c' =&gt; 'Company',
        'a' =&gt; 'Another Columbia Asia Hospital',
        'ad' =&gt; 'Advertisement',
        'an' =&gt; 'Another Doctor',

);
$step1['questions']['learn_abt'] = array (
        '#type' =&gt; 'radios',
        '#title' =&gt; t ( 'In How did you first learn about the Hospital' ),
        '#options' =&gt; $opt,


);
I somehow fixed the issue. Normally if it is not a required field we don't need to add the following code.


  '#required' => FALSE,


But adding this code fixed my issue. Please let me know if there is any better or correct way to fix this.