Acertain species of animal represents just 3 percent of the biomass in its ecosystem. we might classify this as a keystone species if its elimination

Keystone species are those species on which organisms living in that ecosystem largely depend upon. Elimination of keystone species can lead to adverse effects on the organisms living there and the diversity of that community gets decreased. Thus. a keystone species play an important role in maintaining the stability in the ecosystem. 

Iam not sure but to me it with be a or dsorry if i was late! hope this ! : )if you really want me to find out the answer that is correct tell me and i will do more research but the a or d makes sense to me.