When calculating the mean value, what is the recommended approach regarding the use of the calculated standard deviation for determining the number of significant digits to include?

A) Include all digits of the standard deviation in the mean value.
B) Round the mean value to the same number of decimal places as the standard deviation.
C) Include only the significant digits of the standard deviation in the mean value.
D) Disregard the standard deviation when determining significant digits for the mean value.