Sometimes human use of resources is good. Sometimes human use of resources causes damage. We need to make smarter decisions to protect our neighborhood.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.