Correct Answer - A
Number of milleequivalent of `HCl`
`=20xx0.050xx1=1`
Number of millequivalent of `Ba(OH)_(2)`
`=2xx30xx0.1=6`
milliequivalent of `Ba(OH)_(2)`
`[OH^(-)]` of final solution `=` (milliequivalent of `HCl`)/(total volume)
`=(6-1)/(50)=0.1 M`