In the Following Proof, Which Justification Is Correct for Line

Multiple Choice

In the following proof, which justification is correct for line 7? $\begin{array}{llcc} \text {(1) \( (x) (\sim \mathrm{N} x \supset \mathrm{B} x) \) } && \text {Premise } \\ \text { (2) \( (\exists y) \sim \mathrm{By} \) } & \text { \(I(\exists z) (\mathrm{N} z \quad \vee \sim \mathrm{C} z) \) } & \text { Premise/Conclusion } \\ \text { (3) \( \sim \mathrm{Ba} \) } &&2 \mathrm{EI} \\ \text {(4) \( \sim \mathrm{Na} \supset \mathrm{Ba} \) } && 1 \mathrm{UI} \\ \text {(5) \( -\mathrm{Na} 3 \) , } &&4 \mathrm{MI} \\ \text {(6) \( \mathrm{Na} \) } &&5 \mathrm{DN} \\\text { (7) \( \mathrm{Na} v \sim \mathrm{Cba} \) } &\\\end{array}$

A) 4 Imp
B) 6 Add
C) 6 Taut
D) Assumption
E) None of these answers are correct.