I believe the answer is A hope this helps :)
Scientist study index fossils so they will get an understanding of what life was like back then.
Answer:
large grain sizes, more precipitation, warmer temperatures.
Explanation:
Soil is the thin layer of material covering the earth's surface and they are usually formed through the process of weathering of rocks. The soil consists of mainly mineral particles, organic materials, air, water and living organisms and they interact with each other.
Large grain sizes, more precipitation, warmer temperatures are the factors that increase the rate of soil formation.