Supply-side economics believes in the national economy

Supply-side economics believes in the national economy growing most vigorously both through reducing taxes, especially taxes affecting large movements of capital, and by the elimination of the regulations that prevent business from performing optimally.
(A) in the national economy growing most vigorously both through reducing taxes, especially taxes affecting large movements of capital, and by the elimination of
(B) in the national economy most vigorously growing both through the reduction of taxes, especially taxes affecting large movements of capital, and eliminating
(C) that the national economy grows most vigorously through both reducing taxes, especially taxes affecting large movements of capital, and eliminating
(D) that the national economy grows most vigorously both through the reduction of taxes, especially taxes affecting large movements of capital, and also the elimination of
(E) for the national economy to most vigorously grow both through reducing taxes, especially taxes affecting large movements of capital, and eliminating

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https://magoosh.com/gmat/2012/gmat-idiom ... ieve-that/