To solve this problem, we need to understand the sequence of reactions involving urea, water, and copper ions.$\newline$1. Urea reacts with water to form ammonia and carbon dioxide:$\newline$• The reaction is:$\newline$CO(NH$_2)_2 + H_2O \rightarrow 2NH_3 + CO_2 \newline$2. The ammonia (NH$_3$) produced can react with water to form ammonium ions:$\newline$• NH$_3 + H_2O \rightarrow NH_4^+ + OH^- \newline$3. When ammonia is passed through a solution containing copper ions (Cu$^{2+}$), a complex is formed:$\newline$• The deep blue color is due to the formation of the complex ion $[Cu(NH_3)_4]^{2+}. \newline$• The reaction is:$\newline$Cu$^{2+} + 4NH_3 \rightarrow [Cu(NH_3)_4]^{2+} \newline$Analyzing the options:$\newline$• Option 1: $[Cu(NH_3)_4]^{2+}$ is the correct formula for the deep blue complex.$\newline$• Option 2: Cu(OH)_2 is not related to the deep blue color.$\newline$• Option 3: CuCO_3 \cdot Cu(OH)_2 is not related to the deep blue color.$\newline$• Option 4: CuSO_4 is not related to the deep blue color.$\newline$Therefore, the correct option is Option 1: $[Cu(NH_3)_4]^{2+}.$