What indicates the start and end of an element in XML?

In XML, the structure and syntax are defined primarily by the use of tags, which clearly indicate the beginning and end of an element. An element starts with a start tag, which is formatted as , and ends with an end tag, formatted as . This tagging system provides a clear hierarchical structure to the data, allowing parsers to interpret and manipulate the data effectively.

Using brackets, commas, or colons would not align with XML syntax or structure. Brackets could cause confusion as they are not used in the definition of XML elements, while commas and colons do not have any special meaning or role in XML format. Therefore, the use of start and end tags is fundamental and is what makes option A the correct choice.