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Hi,I would like to know if it's possible to add an other(please specify) option in the ranking question type.Regards,
Satyam 

You only have to check if your code "6" is in one of the answers, meaning 
"Is it on rank_1 or rank_2 or rank_3 or ..."
This is the condition to display the text question.

But this approach is really not advisable.
How do you want to analyze it?
Furthermore that there is no full ranking.
How do you calculate the not selected options? Do they get the median of all not used ranks? Or which other value?
And which information do you get if an "Other" option is entered in 2% of all reponses? You can't compare with the precoded options, to be honest, you can't do anything, only list them.

Therefore we always tell out customers to add an open question "Is there something else that is important?"

Joffm