Proposition 1A Given the Following Proposition

Multiple Choice

Proposition 1A
Given the following proposition:
[A ⊃ ∼ (B • Y) ] ≡ ∼[B ⊃ (X • ∼ A) ]
-In Proposition 1A, the main operator is a:

A) Tilde.
B) Wedge.
C) Triple bar.
D) Dot.
E) Horseshoe.