The heat flow due to the mass motion of a fluid or gas is accomplished by O conduction
O convection
O radiation
all of the above

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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.