Answer : A
Lets consider 1st Mux
select line is given as Z
if we consider Z(Select Line) as 1 then input line is going to be selected as 1 a/c to given Mux diagram which is y'
if we consider Z(Select Line) as 0 then input line is going to be selected as 0 a/c to given Mux diagram which is x
Let say output of 1st Mux is A = y'z + xz'
Now Lets consider 2nd Mux
if we consider Y(Select Line) as 1 then input line is going to be selected as 1 a/c to given Mux diagram which is x
if we consider Y(Select Line) as 0 then input line is going to be selected as 0 a/c to given Mux diagram which is y'z + xz'
xy + y'(xz'+y'z)
xy + xy'z' + y'z
y'z + x( y+ z')
xy + xz' + y'z