1 Pretest: Unit 4 Question 2 of 23 Which of the following is a characteristic of all parallelograms? O A. Consecutive angles are congruent. OB. There are 4 right angles. C. Both pairs of opposite sides are congruent. d. the diagonals are perpendicular​

C. a,b, and d are not numbers. they are expressions.

  example you can find the perimeter by addig all of its respective sides as such: (12+x)+(12+x)+(7+y)+(7+y).  adding like terms will result in   2x+2y+38    if you chose  xy+7x+12y+84, you multiplied the two sides to find the area.  if you chose  x+y+19