The correct answer is B) 2.8 feet. To determine the remaining righting arm at 30° inclination, you need to use the stability curves in the blue pages of the Stability Data Reference Book. Given the vessel's drafts and KG, you can locate the appropriate stability curve and read off the righting arm at 30° inclination. Since the center of gravity is 0.9 foot off the centerline, you need to adjust the righting arm accordingly. The stability curves provide the righting arm for a centered center of gravity, so you need to reduce the righting arm by 0.9 foot, resulting in a remaining righting arm of 2.8 feet. The other options are incorrect because they do not accurately reflect the righting arm based on the provided information.