The quadrilateral formed by joining the mid-points of the sides of a quadrilateral taken in order is a rhombus if
diagonals of are equal.
We know that is a rhombus
So
Now,
Since and are midpoints of and
By midpoint theorem,
we get
Since and are midpoints of and
By midpoint theorem
we get
Now, again, is a rhombus
⇒
⇒
Hence, diagonals of are equal
therefore, option is correct.