Imagine you are given the following four measuring instruments:
A. A micrometer, which is a special instrument used by engineers to accurately measure to the nearest millimeter or even more precisely.
B. A 30 cm ruler, which is the ruler you usually use in school.
C. A stick exactly one meter long.
D. An odometer, which is an instrument used in a car to measure distances in kilometers.
Which instrument would you use to measure the length of your index finger?