Cells require a structure that regulates the transfer of material in and out of the cell. This structure is the - cell membrane.
mitochondria.
nucleus
chloroplast

A.) cell membrane

Explanation:

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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.