HTML survey import - how do you add text entry in multiple choice questions?

I want to create a multiple choice question where one of the options is free text entry (e.g. Other: __________). However, I am importing my survey from a .txt file. How do I write this command into the .txt file? It currently looks like this: [[Question:MC:SingleAnswer:Vertical]] [[ID:Gender]] What gender do you identify as? [[Choices]] Female Male Other <---- this is where I want text entry