The sensitivity of a measuring instrument is the value of the smallest quantity that can be read or estimated with it. What is the smallest part of a centimeter that can be read with the following?

(a) a meterstick with markings at each millimeter.

(b) a digital caliper with a four-digit display

I've got an answer for (a) which was 0.05cm, and tried the following for (b) but none was correct:

0.0001cm, 0.01mm, 0.002mm