Question

Which of the following is not a standard unit of length?

• A. Kilometer
• B. foot
• C. centimeter
• D. millimeter

Answer 1

The correct option is B

foot

Correct option is B: foot

Explanation of incorrect option::

1. Standard unit of length is meter.
2. $1kilometer=1000meter$. Hence, kilometer is also a standard unit of length.
3. $1milimeter=\frac{1}{1000}meter$. Hence, millimeter is also a standard unit of length.
4. $1centimeter=\frac{1}{100}meter$. Hence, centimeter is also a standard unit of length.

Explanation of correct option:

1. $1foot=0.3048meter$. Hence, foot is not a standard unit.

Final Answer: Option B