Answer:
B. The diagonals are congruent.
Step-by-step explanation:
Let's review each proposed answer.
A. The opposite angles are congruent (equals).
That is true for ALL parallelograms.
B. The diagonals are congruent
This is true only for rectangles. That also means that the angles are all rectangle angles (90 degrees).
C. The opposite sides are parallel.
This is also true for all parallelograms (hence the name of the figure)
D. The consecutive sides are congruent
If that's the case, you have a lozenge figure, which could be a square or not.