According to the solar nebula theory, planetary development in the solar nebula began with:
A) the growth of dust grains.
B) the formation of ice caps.
C) the fission of helium atoms.
D) the fission of hydrogen atoms.
Question 2
The ice line is:
A) the freezing point of water in Venus's atmosphere.
B) a region in Mars beyond which liquid water exists as permafrost.
C) a boundary in the Solar System beyond which the water vapor could freeze.
D) the temperature at which the ice in the polar caps of Mars turns into liquid water.