Which of the following ion is necessary for the contraction of a muscles and nerve impulse transmission [CPMT 1995; RPMT 1995; BHU 2005]

• A. \[N{{a}^{+}}\]
• B. \[{{K}^{+}}\]
• C. \[C{{a}^{++}}\]and\[M{{g}^{++}}\]ions
• D. None of these