____________ refers to that site which has previously been used and has become derelict. It has to be made safe before it can be used for development.

Correct option is C

A Brownfield site refers to land that has been previously developed, often for industrial or commercial use, and has since become derelict or contaminated. Before it can be reused or redeveloped, the site needs to be cleaned up and made safe, often due to pollution or hazardous materials.
Information Booster:
· Brownfield sites are often located in urban areas where land is scarce, and redevelopment can offer opportunities for revitalizing neglected spaces. Cleaning up these sites can be expensive, but it helps mitigate environmental hazards and make the land usable again.
· Governments and developers often work together to reclaim and repurpose these sites for new housing, commercial, or industrial projects.
Additional Knowledge: 
Greenfield site: Incorrect. A Greenfield site refers to undeveloped land, typically in rural or semi-rural areas, that has not been previously built on.
Yellowfield site: Incorrect. This term is not commonly used in the context of site development.
Redfield site: Incorrect. This term is not standard in land-use planning or site development.