My answer is D. Both the square and parallelogram are quadrilaterals because they both have four sides. Both the sides of the square and parallelogram's are parallel because they are facing each other. The trapezoid only has one pair of parallel sides, which is its top and bottom.
The angles on a straight line add up to 180. The angles on parallel lines also add up to 180. This figure is a parallelogram.
No, I do not agree with this statement. This is because squares have all four equal-length sides, whereas parallelograms do not have four equal-length sides.