What category of classified military information (CMI) is associated with classified U.S. data requested by a foreign ally involved in radar research?

The correct category for classified military information (CMI) associated with classified U.S. data requested by a foreign ally involved in radar research is applicable to a focus on research and development. Specifically, Category 3 encompasses Applied Research and Development Material, which is particularly relevant when discussing advanced technologies and systems like radar.

This category includes information related to the development of military capabilities and the application of innovative technologies. When a foreign ally requests classified information in the context of radar research, it pertains to their understanding and use of these advanced military techniques, solidifying the relevance of applied research in defense systems.

The other categories do not fit this context as precisely. Personnel Security concerns the safeguarding of sensitive personal information related to individuals; Military Materiel and Munitions focuses on physical military equipment and weapon systems rather than research data; and Technical Data can include broader types of information about technology but does not specifically encapsulate the focused research aspects highlighted in radar developments. Thus, Category 3 is the most appropriate for this situation.