1. URL generated in Zoho CRM with a specific custom variable, 
2. to Zoho Survey, and then when the Survey gets submitted, 
3. I want a checkbox to be checked in the CRM

How would I form the custom variable to do so?  I have no problem doing the above with actual text  (passing the word "yes" from Zoho CRM, invisibly to Survey, and then back into Zoho CRM to update a field with the word "yes").....but I want to know how to check a checkbox in the CRM, not add a word.