(A ⊃ B) ⊃ {(C ⊃ D) ⊃ [(∼A ⊃

Multiple Choice

(A ⊃ B) ⊃ {(C ⊃ D) ⊃ [(∼A ⊃ C) ⊃ (∼D ⊃ B) ]}
Which of the following propositions is a proper assumption for conditional proof to prove that the above wff is a logical truth of PL?

A) (A ⊃ B) ⊃ {(C ⊃ D) ⊃ [(∼A ⊃ C) ⊃ (∼D ⊃ B) ]}
B) (A ⊃ B) ⊃ {(C ⊃ D) ⊃ [(∼A ⊃ C) ⊃ ∼D]
C) (A ⊃ B) ⊃ {(C ⊃ D) ⊃ (∼A ⊃ C)
D) (A ⊃ B) ⊃ (C ⊃ D)
E) A ⊃ B