Which choice can be used to confirm that a quadrilateral is a parallelogram
a. quadrilateral is a parallelogram if it has two pairs of parallel sides
b. a quadrilateral is a parallelogram a good has two congruent sides and two non-congruent sides
c. a quadrilateral is a parallelogram if it has two adjacent congruent angles
d. quadrilateral is a parallelogram if it has opposite angles that are not congruent

Girardo is using the model below to solve the equation . girardo uses the following steps: step 1 add 4 negative x-tiles to both sides step 2 add 1 negative unit tile to both sides step 3 the solution is which step could be adjusted so that gerardo's final step results in a positive x-value? in step 1, he should have added 4 positive x-tiles to both sides. in step 1, he should have added 3 negative x-tiles to both sides. in step 2, he should have added 4 negative unit tiles to both sides. in step 2, he should have added 1 positive unit tile to both sides.