The elastic clause or necessary and proper clause is a clause located within the Constitution. The clause is located in Section 8 Clause 18 of the Constitution. The necessary and proper or elastic clause is important because it grants Congress sweeping powers to make any law that is "necessary and proper" to enforce the constitution. This means that anything not specifically included in the Constitution can be made into a law if the Congress believes that it is necessary to uphold some element of the Constitution.
I am pretty sure it is A
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