4.08 g of a mixture of BaO and unknown carbonate (MCO3) was heated strongly. The residue 3.64 g was dissolved in 1000 mL of 1N HCl.
The excess acid required 16 mL of 2.5 N NaOH solution for complete neutralisation.
Which of the following is the metal M?
(A) K
(B) Na
(C) Ca
(D) Cu