Final answer:
The CRC is a mathematical algorithm computed on the header information of a frame to ensure data integrity.
Step-by-step explanation:
The subject of this question is Computers and Technology, specifically related to networking and data integrity.
The correct answer is d. Header information, checked, footer. The CRC (Cyclic Redundancy Check) is a mathematical algorithm computed on the header information of a frame. When the destination device receives the frame, the calculation is checked to verify the data integrity. If the results of this calculation don't match the CRC in the footer, it indicates that the data was altered in some way.
For example, let's say a computer sends a frame to another computer over a network. The source computer applies the CRC algorithm to the header information of the frame and includes the resulting CRC value in the footer. When the destination computer receives the frame, it performs the same CRC calculation on the received header information. If the calculated CRC matches the CRC in the footer, it means the data was successfully transmitted without any alterations. If the CRCs do not match, it suggests that the data may have been corrupted during transmission.