Given the task definition and input, reply with output. Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.

Possible Duplicate: Do you use 'a' or 'an' before acronyms? Does one use 'a' or 'an' before the word 'X-Ray'? Quite simply, should a sentence read 'a XML report' or 'an XML report'?.

It's 'an XML report', because which form of the indefinite article to use is decided by how the next word is pronounced. In this case, it's pronounced: An ex-emm-ell report 'XML' begins with a vowel sound, 'e', so an is used rather than a.