Number of ions in one litre of pure water is

• A. \[\text{6}.0\text{23 }\times \text{ 1}{{0}^{\text{23}}}\]      
• B.         \[\text{6}.0\text{23 }\times \text{ 1}{{0}^{\text{16}}}\]  
• C. \[\text{3}.0\text{2 }\times \text{ l}{{0}^{\text{23}}}\]                    
• D.  \[1\times \text{1}{{\text{0}}^{-\text{7}}}\]