The term for the acoustic navigation system that maps the sea floor by emitting sound pulses?

• A. Echo Sounder
• B. Sonar
• C. Side-Scan Sonar
• D. Multibeam

Answer: (B)

Sonar is the broad method that uses emitted sound pulses and listens for their echoes to detect features underwater and map the seafloor. This general term covers any system that sends a sound wave into the water and uses the returned signal to determine distance or create an image of what's beneath the vessel. An echo sounder is a specific type of sonar focused on depth measurement with a single downward beam. Side-scan sonar and multibeam sonar are other configurations that use sonar to image large areas or wide swaths of the seabed. The description in the question—a system that maps the seabed by emitting sound pulses—points to sonar as the overarching term, since it encompasses all these approaches and their purpose of mapping the seafloor.