Which of the following statements is true about the median of a trapezoid?

A. The median of a trapezoid is parallel to each base and its length is one-third of the sum of the length of its bases.

B. The median of a trapezoid is equal to half of the sum of the length of its bases.

C. The median of a trapezoid is equal to half of the product of the sum of the length of its bases and its altitude.

D. The median of a trapezoid is equal to the sum of the length of its bases.​