题目

 Leonardo da Vinci (1452~1519) ____ birds kept in cages in order to have the pleasure of setting them free. A. is said to be buying      B. is said to have bought    C. had said to buy           D. has said to have bought 答案：B种子中最重要的结构是(    )，它是幼小的生命体．A.种皮B.胚乳C.胚D.子叶