Teacher:Generate a question which can yield the answer mentioned in the input. Generated question must be answered by the answer provided in input, without using any extra knowledge.
Teacher: Now, understand the problem? Solve this instance: Context : Keyhole Markup Language (KML) is an XML notation for expressing geographic annotation and visualization within Internet-based, two-dimensional maps and three-dimensional Earth browsers.
Answer : XML
Student:
The Keyhole Markup Language is based upon what?