What "constitutional principle" can be found in both constitutions?

Social contract.

Explanation:

The social contract was a concept originated during the enlightenment era. It gives authority and legitimacy to the States and it explains why people should obey the government's choices. Locke said that by confirming each person to live under a certain type of society, they all accept to surrender certain freedoms and adopt some rights to make life in society able.

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the answer is a, salt plain

i think it’s a i hope that right : )