Which of the following operating systems do not require extensions on files to execute a...

 UNIX and Linux are the examples of operating systems that do not require extensions on files to execute a program. UNIX and Linux are operating systems that are based on the same kernel and share many features and commands. UNIX and Linux do not rely on file extensions to determine the file type or function. Instead, they use file permissions and attributes to indicate whether a file is executable or not. File extensions are optional and mainly used for human readability or compatibility with other systems. References : The Official CompTIA IT Fundamentals (ITF+) Study Guide (FC0-U61), page 86.