Why do astronomers think that there may be other advanced civilizations?

The 529 plan is the type of plan. a. financial fid. b. grant. c. tuition savings. d. scholarship

The medium that carries message signals from senders to receivers of communication is

What is the tychonic system? a. a model of the solar system in which all the planets (including earth) orbit the sun b. a model of the solar system in which the planets, moon, and sun orbit earth c. a model of the solar system where the planets orbit the sun, and this system orbits earth d. a model where all the planets and earth are fixed in space and only the sun and moon move e. a model that expands the system to a vast number of galaxies and star systems