Thinking About the Formation of the Solar System, What Trend

Thinking about the formation of the solar system, what trend in composition would you expect to see from the inside to the outside of the asteroid belt?

A) rockier asteroids progressing toward ones with more hydrogen and carbon compounds
B) iron asteroids progressing more toward one with silicates
C) essentially the same composition all the way through
D) asteroids with hydrogen and carbon compounds, progressing toward asteroids made primarily of ice
E) asteroids with hydrogen and carbon compounds, progressing toward asteroids made primarily of iron and silicates