Explanation:

The Unix operating system was primarily developed by **Ken Thompson** and Dennis Ritchie at Bell Labs in the late 1960s and early 1970s. Ken Thompson is widely credited as the principal creator of Unix. Dennis Ritchie contributed significantly by creating the C programming language, which was used to rewrite Unix, making it more portable. The other names listed, Rod Fenson, Ramavart Cathrin, and Jahnson, are not associated with the original development of Unix. Therefore, Ken Thompson is the correct answer among the given options, recognizing his pivotal role in its creation.