A device mounted on a communication satellite which receives, amplifies and re-transmits signals from earth station is

The correct answer is: B. Transponder

A transponder is a device that receives a signal and then retransmits it, often after amplifying it or changing its frequency. In the context of communication satellites, a transponder receives a signal from an earth station, amplifies it, and then retransmits it back to Earth.

The other options are incorrect.

• A track is a path that a satellite follows in orbit around Earth.
• A transistor is a semiconductor device that can be used to amplify or switch electronic signals and electrical power.
• A terminal is a device that is used to connect to a computer or other network.
• None of the above is a device that receives, amplifies and re-transmits signals from earth station.