I'm pretty sure it's railroads, because there's not that many highways in Siberia, the rivers would be frozen over, and there's not a ton of people in Siberia. I'm sorry if I'm wrong.
Answer:
tightly packed group of older stars
large grouping of more than two stars
loose, disorganized star cluster held together by gravity
because the bottom of the ocean is basically unreachable without the right equipment.
Much pollution fills the air because of train s which let off steam that contains chemicals.
Soil would be #4 because it absorbs a lot so I think you put it backwards
