Question

Which of the following can be used as a standard unit for length measurement?

• A. A metre scale
• B. Length of arm
• C. Legth of footstep
• D. Length of a finger

Answer 1

The correct option is A A metre scale

Standard unit of length should be constant and it should not varies from person to person or place to place or time to time.
Length of footstep, length of arm and length of a finger vary from person to person. Thus, they can not be a standard unit for length measurement.
A metre scale is of the fixed length of 1m. Hence, it can be used as standard unit for length measurement.