Given:
In ABCD, AB=BC, AD=CD.
To find:
The additional information that can be included in the figure showing kite ABCD with diagonals AC and BD.
Solution:
We know that, a quadrilateral is a kite if,
1. Two pairs of congruent sides which are adjacent to each other.
2. One diagonal is perpendicular bisector of other.
From the given information, we have two pairs of consecutive congruent sides AB=BC and AD=CD.
ABCD is a kite if it holds the second property, i.e., one diagonal is perpendicular bisector of other.
So, the required additional information is "segment BD is perpendicular bisector of segment AC".
Therefore, the correct option is B.