Which clause is the source of implied powers under the u. S. Constitution?

Answer: The"Necessary and Proper Clause" (sometimes also called the "Elastic Clause")

Explanation: The Necessary and proper Clause gives Congress the power and authority to make laws that are necessary and proper for the country, it also gives Congress the power take necessary steps in terms of law making to guard and guarantee the sovereignty of the United States of America. With this clause, Congress can act in the best interest of the nation. The Necessary and proper Clause was made to give Congress the power to decide whether, when and how to make laws for "carrying into execution" the powers of another arm, with respect for the for the principle of separation of powers.