Question

in the 1920s, ______ equipment was invented to locate objects in the water. radio periscope telegraphy sonar

Explanation:

• Radio is used for wireless communication.
• A periscope is used for viewing over or around obstacles.
• Telegraphy is a method of long - distance communication.
• Sonar (Sound Navigation and Ranging) uses sound waves to locate objects in water.

Answer:

sonar