If We Were to Intercept a Strong Radio Signal at 1420

Multiple Choice

If we were to intercept a strong radio signal at 1420 MHz in binary format from another civilization, this would be an example of

A) a signal used for communication between a civilization's home world and another planet in its own planetary system
B) a signal used for local communication in the world where the intelligent beings exist
C) an intentional signal beacon
D) a signal used for communication between a civilization's home world and another star system