Regular Expression for Matching Any Character: A Comprehensive Guide

The correct answer is D. \s. Here's why:

• \s matches any whitespace character, including spaces, tabs, and line breaks.

Let's break down the other options:

• [a-zA-Z] matches any single lowercase or uppercase letter.
• \w matches any word character (letters, numbers, and underscores).
• \S matches any non-whitespace character.

If you need to match any character, including whitespace, special characters, and even newlines, the most reliable option is \s.