question: Hint: Please answer the question and provide the correct option letter, e.g., A, B, C, D, at the end.
  Question: As shown in the figure, in △ABC, DE ∥ BC, if AB = 7.0, AC = 5.0, AD = 3.0, then DE = ()
  Choices:
  (A) \frac{15}{4}cm
  (B) \frac{20}{3}cm
  (C) \frac{15}{7}cm
  (D) \frac{20}{7}cm