What is the name of the multitasking, multi-user operating system developed by Bell Laboratories?

The correct answer is Unix. Unix was developed in the late 1960s and early 1970s at Bell Laboratories. It is known for its multitasking capabilities, allowing multiple users to run processes simultaneously without interference, and its multi-user features that permit concurrent access to the system by various users. Unix laid the foundation for many other operating systems and has influenced the development of numerous programming languages, software applications, and modern computing practices.

Linux, while also a multitasking and multi-user operating system, is a Unix-like system that originated later as part of an open-source project, making it distinct from the original Unix. Mac OS refers to Apple's operating system, which is built on a modified Unix foundation but is not the original system from Bell Laboratories. COBOL is a programming language rather than an operating system, thus it does not pertain to this question.