Very well tried by all

The OA is 'D'!

(A) Formulas for cash flow and the ratio of debt to equity do not apply to new small businesses in the same way as they do to established big businesses, because they are growing and are seldom in equilibrium.

>> 'They' has no clear antecedant.
(B) Because they are growing and are seldom in equilibrium, formulas for cash flow and the ratio of debt to equity do not apply to new small businesses in the same way as they do to established big businesses.

>> This is wordy. "in the same way as they do to". Otherwise 'they' has no problems. Also, first part modifies formulas, it should be new small business.
(C) Because they are growing and are seldom in equilibrium, new small businesses are not subject to the same applicability of formulas for cash flow and the ratio of debt to equity as established big businesses.

>> This is false comparison. "as established big businesses". Also, "are not subject to the same applicability of formulas" sounds awkward.
(D) Because new small businesses are growing and are seldom in equilibrium, formulas for cash flow and the ratio of debt to equity do not apply to them in the same way as to established big businesses.

>> Good.
(E) New small businesses are not subject to the applicability of formulas for cash flow and the ratio of debt to equity in the same way as established big businesses, because they are growing and are seldom in equilibrium

>> 'They' has no clear antecedant.
I like full underlined SCs !

(Irrespective of whether I get it right/wrong

)