According to the definition of a parallelogram, which of the following statements is true?
A) A parallelogram is a quadrilateral where all four sides are of equal length and all angles are right angles.
B) A parallelogram is a quadrilateral with opposite sides that are equal in length and opposite angles that are equal.
C) A parallelogram is a type of triangle with all sides equal and all angles equal.
D) A parallelogram is a polygon with only two sides.