What is the boundary that
separates a cell from the inside and outside environment?

Cell membrane, The cell membrane forms a boundary that separates the cellular contents from the outside environment. The cell membrane is capable of receiving and recognizing chemical signals. The cell membrane forms a barrier that keeps all substances that might harm the cell from entering the cell. (Pls mark me as brainliest!)

plasma membrane

The plasma membrane (often called the cell membrane) is a thin flexible barrier that separates the inside of the cell from the environment outside the cell and regulates what can pass in and out of the cell. Internally, the cell is divided into the cytoplasm and the nucleus.

Explanation:

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It would be a rusting car, for sure 

Carbon dioxide is the correct answer