Asubmarine sends sonar signals to the ocean floor. over time, the signals take longer to reflect off of the ocean floor and back to the submarine. explain why this is.

Both radar and sonar locate objects from the echo of a signal that is bounced off the object. Radar uses radio waves, which are a type of electromagnetic energy. Sonar uses the echo principle by sending out sound waves underwater or through the human body to locate objects. Sound waves are a type of acoustic energy. Because of the different type of energy used in radar and sonar, each has its own applications.

The answer is d if you are on edgenuity. 

Ithink that the missing word is mixed