Question

it is desirable that the standards of unit be easily available, invariable, Indestructible and easily reproducible if we use foot of a person as a standard unit of length which of the above features are the present and which are not ?
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Answer 1

Answer:

If a person's foot was used as a standard unit of length then the unit will be variable and destructible as a person's foot length can vary. There can be a very huge difference. This unit will also be very hard to reproduce and a standard value to compare to other units will not be available.

Thus, for this unit none of the features are present. Hence the length of a foot cannot be a standard unit.

Hope this answer helps:)