Keystone species deserve protection because these
(a) are capable of surviving in harsh envinmental conditions
(b) indicate presence of certain mineral in the soil
(c) have become rare due to over exploitation
(d) play an important role in supporting other species.
(d) : Keystone species is a species which has significant and disproportionately large influence on the community removal or decrease in number of keystone species causes disruption in structure and function of community. For example in intertidal regions star fish feeds on mussels. Removal of star fish leads to dominance of mussels that excludes algae and browsing species. In tropical rain forests fig functions as keystone species as they provide fruit to a number of animal during the period of food scarcity.