(1) 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: (2) the initiation of the successor activity, depends upon the completion ofthe predecessor activity.(3) the initiation ofthe successor activity, depends upon the initiation ofthe predecessor activity.空白（2）处填（）

A. F-S
B. F-F
C. S-F
D. S-S