Which of the following refers to low power modes utilized by microcontrollers to conserve energy?

The term that refers to low power modes utilized by microcontrollers to conserve energy is known as sleep states. When a microcontroller enters a sleep state, it significantly reduces its power consumption by turning off non-essential components and slowly clocking down or suspending its operation. This is particularly crucial in battery-operated devices, where extending battery life is essential.

Microcontrollers often have multiple sleep states, allowing them to balance between performance and power efficiency. These modes enable the device to wake up quickly when needed while ensuring that energy is conserved during inactive periods. This functionality is vital in the context of embedded systems and the Internet of Things (IoT), where efficiency and long operational life are key design considerations.

The other choices—active states, real-time response, and ubiquitous states—refer to operational modes where the microcontroller is fully engaged in processing tasks or is readily available for immediate response and might not emphasize energy conservation in the same way that sleep states do.