The correct option is A Perpendicular to base
Let ABC be an isosceles triangle in which AB=AC
Let →A be the origin of reference and let −−→AB=→b,−−→AC=→c
Let D be the middle point of BC
Then −−→AD=→b+→c2 and −−→BC=→c−→b∴−−→AD.−−→BC=→b+→c2.(→c−→b)=12(|→c|2−|→b|2)=12(|AC|2−|AB|2)=0
Since the two sides are of equal length. Hence, median to the base of an isosceles triangle is perpendicular to the base of the triangle.