Which sentence describes the big bang theory?
 A. Because the universe is expanding, scientists conclude that in the
 distant past, all matter was evenly distributed.
 B. Because the universe is contracting, scientists conclude that in
 the distant future, all matter will be converted to energy.
 C. Because the universe is contracting, scientists conclude that in
 the distant future, all matter will be compressed into a single
 point.
 D. Because the universe is expanding, scientists conclude that in the
 distant past, all matter was compressed into a single point.