The biomass is the plant or animal product or waste which is not used for eating or feeding and is used for generation of energy (in form of heat or other forms). so biomass if source of energy obtained from biological products.
In the given options
Wood : its waste can be used as biomass
Sun : it is the source of solar energy
Manure: it is decomposed product biological material used in agriculture
Water: it is not a source of energy directly
paper : it is also a product of wood but is not considered to be biomass
trash : it depends that what is present in trash and how it can be used
food crops: yes these are biomass
