Scientists have had great success designing and sending rovers to Mars. Rovers are equipped with machinery that allows them to conduct experiments and search for past or present conditions that are favorable for sustaining life. The Curiosity rover, pictured below, is about the size of a car and was designed to transmit and receive signals between Earth and Mars for approximately 23 months.

Scientists on Earth are able to communicate with rovers on Mars through their receivers, which can receive and process signals. Which of these best describes the signals sent and received by rovers?
A.
electromagnetic waves
B.
gravitational energy
C.
potential energy
D.
sound waves