1. Observations show that all galaxies tend to move away from Earth, and that more distant galaxies move away from Earth at faster velocities than do galaxies closer to the Earth. These observations imply that
(a) The Earth is the center of the universe.
(b) The universe is expanding.
(c) The expansion of the universe will eventually stop.
(d) ALL of the above.
2. Which process results in a tremendous amount of energy being emitted by the Sun?
(a) Hydrogen atoms burn in the presence of oxygen- that is, hydrogen atoms oxidize.
(b) The Sun contracts, decreasing its gravitational potential energy.
(c) Protons in hydrogen atoms fuse, forming helium nuclei.
(d) Radioactive atoms such as uranium, plutonium, and cesium emit gamma rays with high energy.
(e) None of the above.