On which story its not here?
The options listed are not related to the question. and if they were related in any sense then I would say the cheapest thing on the list is a phone card so I guess you can buy that and save the most for your travel as you can use phone cards anywhere as they have 1800 numbers which are free from any public phone.
XML (eXtensible Markup Language) is a meta-language that defines a language (of your creation, within XML specs). The language that you create has to follow your specifications.