The planets all lie in nearly the same plane resulting in a disk-like structure for the solar system. This disk-like structure is believed to exist because
a. the solar nebula from which the planets formed had a disk-like structure.
b. the bipolar flow from the young Sun cleared all material out of the nebula except that in the disk.
c. Jupiter's gravity was great enough to pull all of the other planets to the plane of its orbit.
d. the Milky Way Galaxy from which the planets condensed has a disk-like structure
Question 2
If the terrestrial planets were formed by homogeneous accretion, then
a. they were initially molten forming an iron core first, then they accreted a silicate crust later.
b. they were initially molten forming a silicate core first, then they accreted an iron crust later.
c. they were initially collections of solid particles which melted then differentiated into a high-density iron metal core and low-density silicate crust.
d. they were initially collections of solid particles which melted then differentiated into a high-density silicate core and low-density iron metal crust.