胚盘是指位于蛋黄上方,分明区(胚盘中央呈透明状态的区域)、暗区(明区周围呈不透明的区域)。为受精蛋。
参考答案:对
Questions 27~30
A. It has a tutorial supervision system. B. It has progressive ideas on education. C. Its professors are more interested in research. D. Its staff maintain a good relation with the students.
轴承在涡轮增压器中居重要地位,它应保证()。Ⅰ.转子的平衡合格;Ⅱ.可靠地高速回转;Ⅲ.转子运转平稳;Ⅳ.准确固定转子位置;Ⅴ.转子与定子的间隙符合要求。
A.Ⅱ+Ⅲ+Ⅳ
B.Ⅰ+Ⅱ
C.Ⅰ+Ⅱ+Ⅴ
D.Ⅰ+Ⅱ+Ⅳ