Answer:
Biomass
Step-by-step explanation:
By oil, I'm guessing you mean crude oil. Crude oil is a finite resource which is quickly running out because of the consumption of fuels in cars and its other uses as other hydrocarbons. By biomass, I'm guessing you mean biofuel? Biofuel is abundant as it is fuel created through burning crops and plants which is sustainable as we can always grow more plants.
If I have assumed wrong, please reply with a more clearer explanation and I'll be more than happy to help.