ANS:D - 90

The octane number of reformed gasoline, particularly unleaded, can reach up to 90. Here’s why:

1. Reforming Process: Catalytic reforming is a refining process that aims to increase the octane rating of gasoline by rearranging hydrocarbon molecules. This process typically produces high-octane components such as aromatics and iso-paraffins.
2. Octane Number: The octane number is a measure of a fuel's resistance to knocking during combustion in an engine. Higher octane numbers indicate a higher resistance to knocking, which allows for higher compression ratios in engines without premature ignition.
3. Achievable Octane Ratings: Through catalytic reforming, modern refineries can produce unleaded gasoline with octane numbers reaching up to 90 or even higher. This high-octane gasoline is crucial for meeting the performance requirements of modern, high-efficiency engines.