Where did Sir Tim Berners-Lee develop HTML?

Sir Tim Berners-Lee developed HTML while he was working at the Center for European Nuclear Research (CERN) in the late 1980s and early 1990s. At CERN, Berners-Lee sought to create a system that could facilitate information sharing among researchers, which led to the formulation of the World Wide Web and the development of HTML (Hypertext Markup Language) as a foundational technology for creating web pages. This work at CERN was crucial, as it laid the groundwork for the internet as we know it today, making information accessible across various platforms and devices. The environment at CERN, which was focused on high-energy physics research and involved many scientists in need of a more efficient way to communicate, was key to the conception and implementation of his ideas. This context is what makes the Center for European Nuclear Research the correct answer.