What is a disadvantage of using biomass that the other types of alternative fuels do not have?

1)Agricultural wastes will not be available if the basic crop is no longer grown. 2)Additional work is needed in areas such as harvesting methods. 3)Land used for energy crops maybe in demand for other purposes, such as faming, conservation, housing, resort or agricultural use. 4)Some Biomass conversion projects are from animal wastes and are relatively small and therefore are limited. 5)Research is needed to reduce the costs of production of Biomass based fuels. 6)Is in some cases is a major cause of pollution.

Ido not understand. 

The answer is b because c don't explain why the moths are on them and it isn't a because as we know only one species of moth does this