Correct Answer - D
Let `h=`final height of liquid
Equanting the volume we have
`Ah_(1)+Ah_(2)=A(2h)`
`:. h=(h_(1)+h_(2))/(2)`
`W_(mg)=-Delta U=U_(i)-U_(f)`
`= [(Ah_(1)rhog.(h_(1))/(2))+(Ah_(2)rhog.(h_(2))/(2))]`
`-[2A((h_(1)+h_(2))/2)rho((h_(1)+h_(2))/4)]`
Simplifyig this expression we get the result.