Choice "C" is correct. A cold site is an off-site location that has all the electrical connections and other physical requirements for data processing, but does not have the actual equipment.
Choice "b" is incorrect. A hot site is an off-site location that is fully equipped to take over the company's data processing.
Choice "d" is incorrect. A warm backup site is a facility that is stocked with all the hardware necessary to create a reasonable facsimile of the primary data center. The warm backup site is the compromise between the hot backup site and the cold backup site.
Choice "a" is incorrect. Flying start is not a method of disaster recovery.