Answer:
The Necessary and Proper Clause, also known as the Elastic Clause, is a clause in Article I, Section 8 of the United States Constitution: The Congress shall have Power. The Supremacy Clause of the Constitution of the United States, sets up that the Constitution, government laws made in accordance with it, and arrangements made under its power, establish the "incomparable Law of the Land", and in this manner take need over any clashing state laws.
Answer: Supreme Justices serve for life because of "good behavior."
Explanation: Since, 1787 the Constitution has granted Supreme Justices to serve for life or until they retire.