Final answer:
The most widely used embedded operating system among the options listed is eCos (B). eCos is an open-source, configurable OS optimized for embedded systems that require efficient resource use. Option B is correct.
Step-by-step explanation:
Embedded operating systems are specialized OS that are designed for use in embedded computer systems. They are compact and efficient, enabling dedicated applications to run on hardware-constrained devices. The question asks which of the options listed is one of the most widely used embedded operating systems.
The correct answer is B) eCos. eCos (Embedded Configurable Operating System) is an open-source, free, and highly configurable operating system designed for embedded systems and applications which requires a scalable and flexible OS. It is known for its configurability and for being lightweight, which is particularly important in embedded systems where resources are usually limited. While TinyOS is also a significant player in the domain of embedded systems for sensor networks and low-power devices, eCos is widely recognized and used across different types of industries and embedded applications.
Options A) API, C) TinyOS, and D) MQS are either not operating systems or not as widely recognized as eCos in the context of embedded operating systems.