Which term is described by 'sum to check data'?

• A. Check digit
• B. Echo check
• C. Error detection
• D. Parity check

Answer: (D)

This question tests a sum-based error-detection method, where an extra bit is used so the total number of ones in the data has a fixed parity (even or odd). The receiver re-checks by summing the bits and comparing to that parity; if the count doesn’t match, an error is detected. This precise technique is called a parity check. A check digit is a different mechanism that adds a special digit to a number to catch mistakes in that number, and an echo check or broader error-detection category refers to other approaches, but parity check specifically uses the sum of bits to verify data integrity.