The correct response is:
The polyvinyl wrap probably caused the browning since it traps ethylene gas which would speed up the ripening process.
Ethylene gas is a naturally occurring plant hormone that promotes ripening in fruits. The polyvinyl wrap is known to trap ethylene, which would lead to an acceleration of the ripening process and, consequently, more browning of the banana half. In contrast, polyethylene wrap is more permeable and allows ethylene gas to escape, which would help delay the ripening process.