What is a Sensor?

• A. A policy document
• B. A storage unit
• C. A calculation function
• D. A measuring or recording device

Answer: (D)

A sensor is a device that detects a physical property (like temperature, pressure, light, or motion) and converts that information into an electrical signal or digital data that can be measured, recorded, and analyzed. This makes sensors essential for gathering real-time data in digital systems, enabling monitoring, control, and informed decision‑making. For example, a temperature sensor in a building provides readings to a thermostat to regulate climate.

The other options don’t fit because a policy document sets rules and guidelines, not measurements; a storage unit holds data but does not sense or measure anything; a calculation function performs computations on data but does not capture new data from the environment.