Based on what you know about the possibilities of communicating with distant civilizations, select all of the correct statements from the following list. Even radio messages would take years to travel between planetary systems. Since we have not yet been in contact, most astronomers think that it is no longer a reasonable possibility that other civilizations exist in our galaxy, and that SETI should be abandoned. Broadcasting messages in mathematical patterns is a way for radio signals sent by technological civilizations to be distinguished from signals from natural sources. The limiting factor in communicating with other technological civilizations may be the lifetime of such civilizations. The "water hole" is one specific radio wavelength where radio signals that are technological in origin are likely to be found. The SETI program concentrates its searches on this water hole. Because of the distances involved, interstellar travel is not a viable means of communication.