Abcd is a parallelogram and line cd = line da. determine whether the parallelogram is a rhombus. if so by which property?
a. rhombus; perpendicular diagonals property, b. rhombus; congruent adjacent sides property, c. rhombus; bisected angles property, d. not a rhombus

Since it tells you it's a parallelogram you know that opposite sides are parallel.
The other piece of information we are given is a pair of consecutive congruent sides. If these sides are congruent the other sides must also be congruent.
Letter B is the answer

Option: B is the correct answer.

    B.  Rhombus; congruent adjacent sides property.

Step-by-step explanation:We know that a parallelogram is a quadrilateral which has two pair of parallel sides.Also, a parallelogram will be called a rhombus if all the sides are of same length.That is we may say that a Rhombus is a parallelogram but a parallelogram need not be a rhombus.

We are given that:

ABCD is a parallelogram ( this means AB||CD and BC||DA ) and line CD = line DA.

Hence,  the parallelogram is a rhombus by:

            Congruent adjacent sides property.

You have to give us options

This is too long-standing now get out