Correct Answer - A
The problem is valid only if strong acids are mixed. After mixing equal volumes of three acids, total volume `=3V`.
`:. [H^(+)]` after mixing
`=(10^(-3)xxV)/(3V)+(10^(-4)xxV)/(3V)+(10^(-5)xxV)/(3V)=(1.11xx10^(-3))/(3)`
`=3.7xx10^(-4)`