The repeating subunits that are responsible for the shape of a crystal are known as

A crystal has a specific pattern, has a short range order. The repeating subunits that are responsible for the shape of a crystal are known as crystal lattice. 

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.

catya your not at all which answer i've seen you do this on another question!