These three areas are found in a biosphere reserve:-
A) Core zone includes the interior region of biosphere where the natural environment is maintained, biodiversity and the genetic complex is protected and human activity is forbidden.
B) Buffer zone includes the area which surrounds the core area. The activities which are allowed, they help to protect it.
C) Manipulation zone is the outermost area of the biosphere reserve. Several human activities like settlements, cropping, recreation, and forestry are carried out in such areas without disturbing the environment.
So, the correct answer is 'Core zone'.