1 . ∅

• A. $\left\{x+iy\right\}$
• B. $\left\{x+iy;x,y\in R\right\}$
• C. $\left\{2i, 3i.....\right\}$
• D. $\left\{i, \pm 3i,2\right\}$

Answer: Option B

Explanation: