# Question and Answer Data
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**Topics**
+ [Crowd HTML Elements](ApiReference_HTMLCustomElementsArticle.md)
+ [Using XML Parameter Values](ApiReference_XMLParameterValuesArticle.md)
+ [HITLayout](ApiReference_HITLayoutArticle.md)
+ [HTMLQuestion](ApiReference_HTMLQuestionArticle.md)
+ [ExternalQuestion](ApiReference_ExternalQuestionArticle.md)
+ [QuestionForm](ApiReference_QuestionFormDataStructureArticle.md)
+ [QuestionFormAnswers](ApiReference_QuestionFormAnswersDataStructureArticle.md)
+ [Formatted Content: XHTML](ApiReference_FormattedContentXHTMLArticle.md)
+ [AnswerKey](ApiReference_AnswerKeyDataStructureArticle.md)
+ [Data Structure Schema Locations](ApiReference_SchemaLocationArticle.md)

 The questions and answers that Amazon Mechanical Turk passes between Requesters and Workers are XML documents that conform to schemas. These documents are passed to the service and returned by the service as parameter values.