Which of the following is NOT a popular CI/CD application?

The correct answer is based on a fundamental understanding of continuous integration and continuous deployment (CI/CD) applications. Jenkins, Travis CI, and Drone CI are all well-known tools within the CI/CD ecosystem that facilitate automation in coding, testing, and deployment processes. These tools are widely used by developers to streamline their software development workflows, allowing for quicker and more reliable releases.

On the other hand, Photoshop CI does not pertain to CI/CD at all. It references an application related to graphic design (Adobe Photoshop) rather than a development automation tool. As such, it lacks the relevant features and capabilities that are essential for CI/CD practices, making it the outlier in this list of options. Understanding the context of these applications is essential for grasping the principles of modern software development practices.