Nine descriptions about error checking methods are given in the table below. By ticking (✓) in the appropriate column or columns, indicate whether each description refers to checksum, parity check, ARQ or CRC. It is possible more than one column, or none of the columns, can be ticked for each statement.

Description An extra bit is sent with each byte of data. Makes use of positive and negative acknowledgement. Uses timeout to determine if data needs to be re-sent. If an error is found, a request is made to re-send the data. Re-calculation is made on any additional data values sent with the main data block. Method used to determine which bit in a data block has been altered. Additional value sent at the end of a block of data used to check if a data transmission error occurred. Number of 1-bits are counted before and after a data block has been sent. Value used as part of a data packet trailer to check if any data corruption has occurred. Checksum Parity check ARQ CRC