The correct option is B y−axis
Let the intercepts of the line are p & q.
Thus it's equation is given by, xp+yq=1
Given line also passes through (a,0), ⇒p=a
So, the coordinates on the axes are (a,0),(0,q).
Let mid point of this segment be (h,k)
∴h=a2,k=q2
So, y=q2,
Since a is given, so x-coordinated is fixed.