Select a Counterexample for the Given Invalid Argument

Multiple Choice

select a counterexample for the given invalid argument.
-1. (∃x) (Mx • Nx)
2) (∀x) (Ox ⊃ Mx) / (∀x) (Ox ⊃ Nx)

A) Counterexample in a domain of 2 members, in which:
Ma: True Na: True Oa: False
Mb: True Nb: True Ob: True
B) Counterexample in a domain of 2 members, in which:
Ma: True Na: False Oa: True
Mb: True Nb: True Ob: True
C) Counterexample in a domain of 2 members, in which:
Ma: True Na: False Oa: False
Mb: True Nb: False Ob: True
D) Counterexample in a domain of 2 members, in which:
Ma: True Na: False Oa: False
Mb: False Nb: True Ob: True
E) Counterexample in a domain of 2 members, in which:
Ma: False Na: False Oa: False
Mb: True Nb: True Ob: False