Final answer:
The phrase identifying the importance of the elastic clause in Article I is 'Necessary and Proper Clause,' which allows Congress to make laws necessary for carrying out its powers, leading to an expansion of Congressional authority.
Step-by-step explanation:
The phrase that identifies the importance of the elastic clause in Article I is A) Necessary and Proper Clause. This clause, found in Article I, Section 8, Clause 18 of the U.S. Constitution, grants Congress the authority to pass all laws deemed necessary and proper for carrying out the enumerated powers. Often referred to as the elastic clause, it has allowed for a gradual expansion of Congressional powers over time. This clause gives Congress the flexibility to meet new needs and address unforeseen issues by creating legislation within the bounds of its constitutional responsibilities.
The elasticity of this clause comes from its ability to stretch beyond the specifically listed powers in clauses 1-17 of Article I, Section 8, which has given rise to implied powers. These implied powers have been upheld by courts as fitting within the scope of the federal government's authority, thus having a significant impact on the power dynamics between the federal government and the states.