Scientists are always learning new things. Which of the following shows how
scientists use observations to gain new understanding about the world?
A. Scientists have discovered new planets orbiting a star by
detecting a wobble in the star's motion.
B. Scientists hope to learn more about how many stars are in space.
C. Scientists wonder if other planets can support life, and some
scientists wonder if there are aliens.
D. Scientists are familiar with some galaxies, but they do not know
how many galaxies exist.