Final answer:
The scalability feature of a MOOC indicates the capacity for unlimited participants or enrollment, designed to support thousands of students using technology for distribution and assessment.
Step-by-step explanation:
The element of a Massive Open Online Course (MOOC) that indicates an unlimited number of participants or enrollment is its scalability feature.
MOOCs are designed to support a vast number of students, often in the thousands or even more, without significant incremental costs for each new participant.
This is in contrast to traditional educational settings with physical or resource limitations that may restrict class sizes. MOOC platforms use technology to distribute course materials and facilitate interactions among a virtually unlimited audience.
Moreover, automated grading systems and peer review processes enable efficient assessment at scale.