A Biosphere Reserve is divided into 3 distinct zones, which are :
1) Core zone : Here in core or natural zone no human activities are allowed so this area is legally protected and undisturbed ecosystem.
2) Buffer zone : The immediate area of surrounding is buffer zone. Here some human activities such as education and research strategies are permitted.
3) Transition zone : Transition zone is the peripheral area of biosphere reserve and human settlement activities such as cropping , recreation and others can be carries out .
So, correct answer is 'Core'.

Core Zone: A Zone of No Human Activity in a Biosphere Reserve

The correct answer is option 'B', the core zone. Let's understand why this is the case.

Definition of a Biosphere Reserve
A biosphere reserve is a designated area that aims to conserve biodiversity while promoting sustainable development. It is typically divided into three zones: the core zone, buffer zone, and transition zone.

Core Zone
The core zone is the innermost and most strictly protected area within a biosphere reserve. It is the zone where no human activity is permitted. The core zone is primarily focused on the preservation of natural ecosystems and the protection of rare and endangered species. It acts as a sanctuary for wildlife and provides undisturbed habitat for the conservation of biodiversity.

Buffer Zone
The buffer zone surrounds the core zone and acts as a transition area between human settlements and the core zone. In this zone, limited human activity is allowed, but it is carefully regulated to minimize negative impacts on the core zone. The buffer zone helps to protect the core zone from external disturbances, such as pollution and encroachment.

Manipulation Zone
The manipulation zone, also known as the transition zone or sustainable use zone, is the outermost zone of a biosphere reserve. It is the area where sustainable human activities are allowed, such as agriculture, forestry, and tourism. The manipulation zone aims to promote sustainable development and community participation while ensuring the conservation of natural resources.

Conclusion
In summary, the core zone of a biosphere reserve is the zone where no human activity is permitted. It is the most strictly protected area within the reserve and is dedicated to the conservation of biodiversity and the preservation of natural ecosystems. The buffer zone and manipulation zone, on the other hand, allow limited human activities while maintaining a balance between conservation and sustainable development.