Which of the following is a configuration management tool?

Puppet is recognized as a configuration management tool because it is specifically designed to automate the administration and management of infrastructure. It allows system administrators to define the state of their systems using a domain-specific language, enabling consistent and repeatable configurations across a large number of servers. Puppet manages resources like files, packages, and services, ensuring that the desired state of these resources is maintained.

In the context of the other options, Docker is primarily a containerization platform that allows developers to package applications and their dependencies into containers. Terraform is commonly classified as an infrastructure as code tool that focuses on provisioning and managing cloud resources rather than directly managing configuration. Jenkins is an automation server, primarily used for continuous integration and continuous delivery (CI/CD), rather than configuration management per se. This distinct focus on automating infrastructure configuration makes Puppet the correct choice in this scenario.