Why is it appropriate to say the Constitution is designed to bend like a willow?

The Constitutions was designed to be flexible so new laws can be added as needed and old laws can be reinterpreted

I believe the answer is: The Constitutions was designed to be flexible so new laws can be added as needed and old laws can be reinterpreted

This mean that the constitution can be reviewed and amendment could be created in order to modify the constitution according to the will of people in society.

Example of an important amendment was the 19th amendment which guarantee women's right to vote because in constitution only men are explicitly given the right to vote.