The gas used for artificial fruit ripening of green fruit is –

Some gases can speed up the ripening process of fruits. Farmers and sellers sometimes use this to make fruits ready for sale quicker.

Out of the options given, ethylene is the gas commonly used for artificial fruit ripening. It's a natural plant hormone that triggers the ripening process. Acetylene, while similar in structure, is less commonly used for this purpose. Ethane and methane are not involved in fruit ripening.

Therefore, the correct answer is Option A: Ethylene.