A substance that is used as a ripening agent for fruits is

Analyze the question: We need the compound used to ripen fruits. This is a well-known property of one particular hydrocarbon.

Explain the concept: Ethene (ethylene, C₂H₄) is a natural plant hormone. Fruits produce it as they ripen, and it triggers the breakdown of starch into sugars, the softening of the fruit, and the change in colour. Because of this, ethene gas is used commercially to ripen fruits such as bananas, mangoes, tomatoes and pawpaw. Fruits picked while still green are often exposed to it before they are sold.

Check each option:

• A. Ethene (C₂H₄): An alkene, and a plant hormone that promotes ripening. ✔
• B. Propane (C₃H₈): An alkane used as a fuel (part of LPG). It has no ripening role.
• C. Methane (CH₄): The main component of natural gas and biogas, used as a fuel. It has no ripening role.
• D. Butane (C₄H₁₀): An alkane used as cooking gas and in lighters. It has no ripening role.

Propane, methane and butane are all saturated alkanes, which are relatively unreactive and are used mainly as fuels. Ethene has a C=C double bond, which makes it chemically active, and it is the only hormone-like gas in the list.

Answer: The correct option is **A.

Tip: Link "Ethene" with "Eat-ripe": ethene makes fruit ready to eat. Also remember that alkenes like ethene are used for ripening and for making polythene, while alkanes are mainly fuels.