Which of the following length measurement is most accurate and why?

Which of the following length measurement is most accurate and why?
(i) 4.00 cm, (ii) 0.004 mm and (iii) 40.00 cm

(i) ∆x /x = 0.01/4.00 = 0.0025

(ii) ∆x / x = 0.001/0.004 = 0.25

(iii) ∆x /x = 0.01/40.00 = 0.00025

The Last observation has the least fractional error and hence, it is more accurate.