In the Following Proof, Which Justification Is Correct for Line

In the following proof, which justification is correct for line 3? $\begin{array}{llcc} \text {(1) \( (x) [(\mathrm{C} x \cdot \mathrm{D} x) \supset \sim \mathrm{E} x] \) } & & \text { Premise } \\ \text { (2) \( \mathrm{Eb} \) } & \text {\(I \sim \mathrm{Cb} \cup \sim \mathrm{Db}\) }& \text { Premise/C onclusi on }\\ \text { (3) \( (\mathrm{Cb} \cdot \mathrm{Db}) \supset \sim \mathrm{Eb} \) } &\\\end{array}$

A) 1 UI
B) 1, 2 MT
C) 1 UG
D) 2 EI
E) None of these answers are correct.