Error detecting code is

• an error-detecting code based on a summation operation performed on the bits to be checked
• a check bit appended to an array of binary digits to make the sum of all the binary digits.
• a code in which each expression conforms to specify rules of construction, so that if certain errors occur in an expression, the resulting expression will not conform to the rules of construction and thus the presence of the error is detected.
• the ratio of the data units in error to the total number of data units
• None of the above