Which of the Following Kinds of Signal Do We Currently

Multiple Choice

Which of the following kinds of signal do we currently have the best chance of detecting with currently technology?

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