Which of the following programs are known web servers?

Apache HTTPD is a well-established web server software that serves web pages to users over the internet. It is widely used and is known for its modular architecture, allowing users to extend its functionality through modules. One of the key features of Apache is its ability to serve both static and dynamic content, making it a versatile choice for various web applications.

NGINX, another choice listed, is also a prominent web server known for its performance and efficiency in handling multiple connections concurrently. It is particularly favored for its ability to serve static files quickly and for its reverse proxy capabilities.

MySQL, on the other hand, is a relational database management system, not a web server. It is used for storing and retrieving data through a database but does not serve web content directly.

Python is a programming language and can be used to develop web applications through various frameworks, but it is not a web server itself. While Python applications can be served using web servers like Apache or NGINX, it does not provide web server functionality on its own.

Thus, Apache HTTPD is a correct identification as a web server, serving HTTP requests and delivering web content to users while the other choices pertain to different functionalities not related to serving web content.