Correct option is D
The least count of a steel rule is 0.5 mm. The least count of an instrument is the smallest measurement it can take. For a steel rule, this is the smallest division on the scale.
Steel rules are made of stainless steel or spring steel and are used to measure distances or draw straight lines. They are available in different lengths, such as 150 mm, 300 mm, and 600 mm. Steel rules can also have metric and English graduations.
Important Points
A micrometer may have a least count of 0.01 mm while a Vernier scale on a caliper may have a least count of 0.02 mm .
