An element M has an atomic mass 19 and atomic number 9; its ions are represented by

• A.  \[{{\text{M}}^{+}}\] 
• B.  \[{{\text{M}}^{2+}}\]  
• C.  \[{{\text{M}}^{-}}\]           
• D.  \[{{\text{M}}^{\text{2}-}}\]