Answer:
b- one diagonal
Step-by-step explanation:
Given parallelogram ABCD, you want to know what additional segments or points will you need in order to prove the opposite sides are congruent.
Parallelogram
The opposite sides of a parallelogram are parallel, so one diagonal is sufficient to allow you to declare pairs of congruent angles using the alternate interior angles theorem.
These let you say the two triangles created are congruent to each other, making opposite sides the same length by CPCTC.
