Why is biomass a better alternative to oil?

This is because biomass is renewable. A new crop can be grown after each harvest, and biomass has  low carbon fuel.

Explanation:

A biomass is a source of thermal energy. It is obtain from burning of the plant and animal material. The materials include the wood, waste obtain from the agriculture land like straw, animal dung and even from the human waste like sewage waste.

Biomass is an alternate source of energy. As the biomass is a renewable source of energy and the oil can be a fossil fuel like crude oil including petroleum, which is a non-renewable source of energy. The biomass energy can be replenished as the plants and animal material can be replenish by the natural cycles. Their quantity will never deplete in nature and they will remain available for the present as well as for the future generation. Whereas, the quantity of oil may deplete in nature as being a non-renewable resource the oil can only be used once and the used amount will not be recovered in any accessible way.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."