Which of the following sensor types uses sound to detect a target?

The correct choice is B, Sonar, as it is specifically designed to use sound waves to detect and locate objects underwater. Sonar operates by emitting sound pulses and analyzing the echoes that return after bouncing off an object. This technology is particularly effective in marine environments, where visual and other forms of electronic detection may be limited.

In contrast, the other sensor types listed function on different principles. Radar utilizes radio waves to detect and track objects, primarily in the air and on land. Infrared sensors detect heat emitted by objects, which is useful for thermal imaging. Optical sensors rely on visible light to capture images or detect objects, functioning effectively in clear environments but not underwater.

Understanding these differences clarifies that sonar is unique in its use of sound for detecting targets, especially in aquatic settings.