The correct answer is: C. .
A metacharacter is a special character that has a special meaning in a programming language or command-line interpreter. The dot (.) is a metacharacter that can be used to refer to any character. For example, the regular expression .* matches any string of any length.
The other options are not metacharacters. The percent sign (%) is a special character in some programming languages, but it does not have a special meaning in regular expressions. The at sign (@) is a special character in some email addresses, but it does not have a special meaning in regular expressions.
Here are some examples of how the dot metacharacter can be used in regular expressions:
.*matches any string of any length..{3}matches any string of three characters..*?matches any string of any length, but the match should be as short as possible.^.*?$matches any string that starts and ends with any character.\.matches a literal dot.
I hope this helps! Let me know if you have any other questions.