Which of the following countries has made it mandatory to blend ethanol with gasoline?

Brazil is the answer, and it is the textbook case. Its mandate goes back to the ProÁlcool programme launched in 1975 after the oil shocks, when the state pushed sugarcane ethanol to cut dependence on imported crude. Anhydrous ethanol has since been blended into all gasoline sold in the country, and the blend level is revised by government notification. At the time of this exam it was around E25 to E27, and it has been raised since, so check the current rule if a question asks for the exact figure.

• China: ethanol blending has run as pilot and provincial programmes, not as a nationwide legal mandate.
• U.K.: fuel standards permit blends up to about 10 percent, but there is no national mandate comparable to Brazil's.
• Switzerland: has no blending mandate, and ethanol use in petrol is marginal.

Core concept: energy security and biofuel policy. For Mains (GS3, energy and agriculture), Brazil's model links the sugar economy, flex-fuel vehicles and import dependence, and it is a useful case in the food-versus-fuel debate.

Trap: aspirants pick the US or China because they produce large volumes of ethanol. Production scale is not the same as a legal blending mandate.