大学英语：there were three groups of oils

1. there were three groups of oils; animal, vegetable and mineral.

油可以分为三大类:动物油,植物油,矿物油.

2. a few other creatures yield oil, but non so much as whale.

有些动物也出油,但都没有鲸鱼出得多.

3. Vegetable oil has been known from antiquity.

植物油从古以来就为人们所熟悉.

4. To it we owe the existence of the motor-car, which has replaced the private carriage drawn by the horse, to it we owe the possibility of flying.

就是因为有了这种油,我们才能用上汽车,以代替马车.就是因为有了这种油,我们才有可能飞行.

5. two metal surfaces rubbing together cause friction and heat; but if they are separated by a thing film of oil, the friction and heat are reduced. No machine would work for long if it were not properly lubricated.

两个金属面相擦,就要产生摩擦和热;但如果在它们之间抹上薄薄的一层油,就可以减少磨擦,降低热度.