Regarding whitespace handling, which statement best describes how XML treats whitespace characters in documents?

Introduction / Context:
Whitespace handling is an important difference between XML and HTML. While HTML rendering often collapses multiple spaces and ignores some whitespace for layout, XML is designed as a data format and by default preserves whitespace in element content. This behaviour allows applications to decide whether whitespace is significant. The question asks you to identify the correct statement about how XML treats whitespace characters such as spaces, tabs, and newlines.

Given Data / Assumptions:

• We are dealing with well formed XML documents.
• Whitespace can appear in element content, attribute values, and between tags.
• Applications that consume XML may treat some whitespace as ignorable based on a Document Type Definition or xml:space attribute.
• We are not confusing XML data processing with HTML visual rendering in a browser.

Concept / Approach:
By default, XML parsers pass whitespace in element content to the application as character data. Whether this whitespace is significant depends on the application and on declarations in the Document Type Definition. XML provides the xml:space attribute and rules in the Document Type Definition that can mark certain whitespace as ignorable. However, XML itself does not collapse, remove, or forbid whitespace automatically. This is a key distinction from typical HTML rendering, where multiple spaces may be visually collapsed into one in a web browser. Therefore, the correct description emphasises that XML preserves whitespace and leaves interpretation to the application.

Step-by-Step Solution:
Step 1: Recall that XML is designed as a markup language for data, not primarily for visual layout. Step 2: Recognise that XML parsers report whitespace in element content as part of the text nodes unless it is declared ignorable. Step 3: Understand that applications may treat certain whitespace as ignorable based on Document Type Definition declarations or xml:space attributes. Step 4: Examine option a, which states that XML preserves whitespace and can mark some of it as ignorable through Document Type Definition or xml:space. Step 5: Reject options that claim XML always collapses, deletes, or forbids whitespace, which are not true of XML processing rules.

Verification / Alternative check:
XML specifications describe whitespace as significant or ignorable and explain how validating parsers use Document Type Definition information to identify ignorable whitespace in element content. Tutorials show that when you read an XML document with a parser, sequences of spaces, tabs, and newlines are delivered to the application unless explicitly marked otherwise. This behaviour confirms that XML preserves whitespace, in agreement with option a, and does not support automatic collapsing or removal as described in other options.

Why Other Options Are Wrong:
Option b describes the behaviour of typical HTML rendering in web browsers, where multiple spaces are collapsed in visual output, but XML itself does not do this; it is up to the application to decide how to handle whitespace. Option c claims that XML completely removes whitespace before processing, which would break many text based applications and contradicts the specification. Option d states that XML forbids spaces, tabs, or newlines in element content, which is incorrect; XML documents often contain formatted text with whitespace.

Common Pitfalls:
A common pitfall is to assume that XML will behave like HTML in terms of whitespace and to design parsing logic based on visual browser behaviour. Another mistake is to forget that formatting whitespace used to indent XML for readability is still present in the document and may need to be treated as ignorable, for example by using a validating parser or by normalising data. For exam answers, remember the simple rule: XML preserves whitespace by default and leaves significance decisions to the application, which is captured in option a.

Final Answer:
XML treats whitespace such that it preserves whitespace by passing it to the application, and it can be treated as significant unless declared ignorable through a Document Type Definition or xml:space settings.