歌剧（）是根据作家（）的同名小说改编，歌颂了民兵队长二黑与村姑小芹争取婚姻自由的故事。
参考答案：《小二黑结婚》；赵树理
（66） is a method of constructing a project schedule network diagram that uses boxes or rectangles, referred to as nodes, to represent activities and connects them with arrows that show the dependencies.This method includes following types of dependencies or precedence relationships: （67） , the initiation of the successor activity, depends upon the completion of the predecessor activity.（68） , the initiation of the successor activity, depends upon the initiation of the predecessor activity.
A．PDM
B．CPM
C．PERT
D．AOA
釉质发育不全常发生在（）
A.下颌第一磨牙
B.上颌第一磨牙
C.对称性的牙
D.上颌侧切牙
E.全口牙
