(Q004) During World War II, the military imaged the seafloor by sending pulses of sound waves down through the water and measuring the time it took for the sound to bounce off the seafloor and return to the receiver. This method is called

Sonar

Explanation:

Sonar is a technique that involves the use of sounds in viewing substances in a water medium to aid movement or communication. It makes use of the advantage of sound waves traveling faster and farther in water when compared to other types of waves such as light waves.

During World War II, the military employed the use of SONAR in imaging the seafloor by sending pulses of sound waves down through the water and measuring the time it took for the sound to bounce off the seafloor and return to the receiver.