The correct answer for this question is B. 12.5%
Since the digit 4cm is in the ones place then you need to take 1 and divide it by 2 to get 0.5cm. Take 0.5 and divide that by the measurement 4cm so 0.5/4 and you get .125 which is 12.5%. Another example would be the finding the percent error of the measurement 12.5 ft. To do so, the last digit is the the tenths place so take 0.1and divide by two to get 0.05. Now take 0.05 divided by 12.5 to get 0.4%.