Accretion among the grains in the solar nebula would have been aided by
a. static electricity.
b. gravity.
c. high-velocity collisions.
d. all of the above
e. none of the above
Question 2
The habitable zone is
a. the region on a planet where conditions are acceptable for life to exist.
b. a region around a star where a planet's temperature would permit the existence of liquid water.
c. very small for a massive star.
d. only found around G and K stars.
e. a region on a young planet where amino acids can begin to form DNA molecules.