Name a popular CSS framework.

Bootstrap is a widely-used CSS framework that simplifies the process of designing responsive and aesthetically appealing websites. It provides a collection of pre-designed components, such as grids, forms, buttons, navigation bars, and alerts, which can be easily integrated into web projects to ensure consistency and speed up development. The framework follows a mobile-first design philosophy, making it particularly effective for creating websites that work seamlessly across various devices and screen sizes.

In contrast, Angular is a platform used for building dynamic web applications, providing a structured approach to developing single-page applications; jQuery is a JavaScript library designed to simplify HTML document traversing, event handling, and animation; and Vue is a progressive JavaScript framework for building user interfaces and single-page applications. All these options serve different purposes in web development and do not classify as CSS frameworks.