This regular expression correctly identifies the structure of an IPv4 address.

- ^ anchors the pattern to the beginning of the string.

- (?:[0-9]{1,3}\.){3} is a non-capturing group that matches a sequence of one to three digits ([0-9]{1,3}) followed by a literal dot (\.). This group is repeated exactly three times ({3}) to match the first three octets (e.g., "192.168.20.").

- [0-9]{1,3} matches the final octet, which consists of one to three digits (e.g., "232").

This combination accurately captures the entire IP address string 192.168.20.232.

B. ^ (?:[0-9]f1,3}\.){1,4}

This expression is syntactically flawed (f1,3}). Even if corrected to {1,3}, it would incorrectly require a trailing dot after the final octet, failing to match the target string.

C. ^ (?:[0-9]{1,3}\.)'

This expression is syntactically incomplete due to the trailing apostrophe. It would only match the initial octets followed by a dot, not the complete IP address.

D. ^ ([0-9]-{3})

This expression is syntactically incorrect. A likely interpretation, ^([0-9]{3}), would only match the first three digits of the IP address ("192"), not the entire string.

---

1. Cisco Systems

Inc.

"Configuring Regular Expressions

" Terminal Services Configuration Guide

Cisco IOS XE Gibraltar 16.12.x. This guide's "Regular Expression Pattern Matching Characters" table defines the metacharacters used in the correct answer

such as ^ (matches at the beginning of the string)

[0-9] (matches a range of single digits)

and . (matches any single character

requiring \. for a literal dot).

2. Python Software Foundation

"re — Regular expression operations

" Python 3.11.4 Documentation. The section on "Regular Expression Syntax" details the usage of quantifiers like {m

n} (matches from m to n repetitions) and the non-capturing group syntax (?:...)

both of which are essential components of the correct regular expression.

3. Guttag

J. V. (2016)

6.0001 Introduction to Computer Science and Programming in Python

MIT OpenCourseWare. Lecture 11 materials on "Regular Expressions" explain the principles of constructing patterns to match specific data formats

such as email addresses or IP addresses

using the fundamental building blocks present in the correct answer.