B 3
4
2
D
C
Melissa writes the following proof for the theorem: If the diagonals of a quadrilateral bisect each other, the quadrilateral is a parallelogram:
Melissa's proof
BO
3. The
1. For triangles AOB and COD, angle 1 is equal to angle 2, as they are vertical angles.
2. AO =
and BO = OD because it is given that diagonals bisect each other.
are congruent by SAS postulate.
4. Similarly, triangles AOD and COB are congruent.
5. By CPCTC AB is equal to DC
6. By CPCTC, AD is equal to BC
7. As the opposite sides are congruent, the quadrilateral ABCD is a parallelogram.
Which is the missing phrase in Melissa's proof?