Answer: a)Significant digit code
Explanation: Significant digit codes are the code that persist a meaning for the number. They are also known as significant figures .They signify the description of any particular quantity with accuracy. Eamon should use significant figures to define features of the location with preciseness.
Other options are incorrect because block sequence code is collection of data on basis of common characteristics , action code is used for reminding the future actions and sequence code is the codes in serial order .Thus, the correct option is option(a).