Select a Counterexample for the Given Invalid Argument

select a counterexample for the given invalid argument.
-1. (∃x) Sx
2) (∀x) [Sx ⊃ (Tx ⊃ ∼Ux) ]
3) Ua • Ub
4) (∃x) ∼Ux / (∃x) (Sx • ∼Tx)

A) Counterexample in a domain of 3 members, in which:
Sa: True Ta: False Ua: True
Sb: False Tb: False Ub: True
Sc: True Tc: True Uc: False
B) Counterexample in a domain of 3 members, in which:
Sa: False Ta: False Ua: True
Sb: True Tb: True Ub: False
Sc: True Tc: True Uc: False
C) Counterexample in a domain of 3 members, in which:
Sa: True Ta: False Ua: True
Sb: True Tb: True Ub: True
Sc: True Tc: True Uc: False
D) Counterexample in a domain of 3 members, in which:
Sa: False Ta: False Ua: False
Sb: False Tb: True Ub: False
Sc: True Tc: True Uc: False
E) Counterexample in a domain of 3 members, in which:
Sa: False Ta: False Ua: True
Sb: False Tb: True Ub: True
Sc: True Tc: True Uc: False