The materials that made up their solar nebula can be categorized into the four general type as follows. rank these materials from left to right based on their abundance in the solar nebula, from highest to lowest.
a) hydrogen and helium gas,
b) hydrogen compounds,
c) rock,
d) metals

Hydrogen and Helium > Hydrogen compounds > Rocks > Metals

Explanation: The solar nebular system contains 98% Light Gases of both Hydrogen and Helium (produced in the Big Bang); followed by 1.4% of Hydrogen Compounds including water, methane, and ammonia; then followed by 0.4% of Rocks like Silicates; and lastly 0.2% of Metals including Iron, Nickel and Aluminium.