Fact 1: Sonar is used to find the location of an object.

Fact 2: Active Sonar Active sonars transmit acoustic energy and detect targets by echolocation.

Given the two facts above, answer the question "what is used to find objects underwater?" with the following options: 
- echolocation
 - a hydraulic system
 - heat energy
 - Electrical energy
 - dolphins
 - mussels
 - by indirect light
 - rays or beams


 

 echolocation        