What Does the Elastic Clause of the U

What does the elastic clause of the U.S. Constitution do?

A) It provides that Congress shall have the power to enact all legislation that is "necessary and proper" to carry out its enumerated powers.
B) It declares that state laws must conform to the federal constitution.
C) It provides that all powers not enumerated to the federal government in the Constitution will be given to the states.
D) It provides that the federal government has power to try criminals who have committed crimes across multiple state boundaries.
E) It allows states to leave the union as long as they may demonstrate just cause.