In the Following Proof, Which Justification Is Correct for Line

In the following proof, which justification is correct for line 4? $\begin{array}{llcc} \text { (1) \( (x) [(\mathrm{C} x \cdot \mathrm{D} x) \supset \sim \mathrm{E} x] \) } && \text {Premise } \\ \text { (2) \( \mathrm{Ea} \) } & \text {\(I \sim \mathrm{Ca} v \sim \mathrm{Da}\) } & \text { Premise/Conclusion } \\ \text { (3) \( (\mathrm{Ca} \cdot \mathrm{Da}) \supset \sim \mathrm{Ea} \) } && \text {\(1 \mathrm{UI}\) } \\ \text { (4) \( \sim \mathrm{Ea} \) } &\\\end{array}$

A) 2 QN
B) 2 DN
C) Assumption
D) 2 Conj
E) None of these answers are correct.