Ava has a gross income of $20,000, and Hal has a gross income of $350,000. Ava's effective tax rate is 14%, and Hal's effective tax rate is 28%. Ava lives in a two-bedroom ranch, while Hal lives in a six-bedroom colonial. Despite the income disparity, they share the same commute. The town's real estate tax is 1.7%. The state's sales tax is 6.35% and the fuel surcharge is $0.59 per gallon. Which tax is regressive? 

O Medicare tax. 

O Fuel tax. 

O Income tax. 

O Real estate tax.