What is the $\mathrm{pH}$ range of concentration of acid produced in the stomach?

Match the digestive glands given in Column - I with their respective enzymes given in Column — II and choose the correct combination from the given options,

Choose the correct option:- 

$100 {\mathrm{cm}}^3$ of  $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ solutions of sodium carbonate and $200 {\mathrm{cm}}^3$ of $0.100 \mathrm{mol} {\mathrm{dm}}^{-3}$ sodium hydrogencarbonate are mixed together to prepare $300 {\mathrm{cm}}^3$ of a buffer solution with $\mathrm{pH} 10.0$. The ${\mathrm{pK}}_{{\mathrm{a}}_2}$for carbonic acid is $10.3$. This buffer solution is mixed with $50.0 {\mathrm{cm}}^3$ of $10.0 \mathrm{mmol} {\mathrm{dm}}^{-3}$ hydrochloric acid. Calculate the $\mathrm{pH}$ of the final solution. Assume that the volume of the final solution is equal to the sum of volumes of initial solutions.