biofuel 是可数名词,复数形式为 biofuels。作不可数名词时,指生物燃料这一类别,如“Biofuel is seen as an alternative to fossil fuel.”;作可数名词时,指具体种类或批次,如“Biofuels such as ethanol and biodiesel”。常见句型包括:主语 + be + biofuel(定义);主语 + produce/use/generate + biofuel(生产使用);biofuel + derived from + 原料(来源)。易错点:不要与 biomass 混淆,后者指生物质原料,而 biofuel 指由其转化的燃料;此外,biofuel 本身不可直接作动词,不能说“to biofuel a car”。