题目：
The (71) is a general description of the architecture of a workflow management system used by the WFMC, in which the main components and the associated interfaces are summarized. The workflow enactment service is the heart of a workflow system which consists of several (72) . In a workflow system, a process is specified using the process definition tool. Usually, processes are defined in terms of a (73) , which consists of (74) indicated using a circle, and (75) shown as a rectangle. These two components can be linked by means of a directed arc.
（73）处填（）。
A．PERT diagram
B．Network Diagram
C．Petri Net
D．Gantt chart
答案：
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参考答案：A,B,C,D解析：结核菌素反应阴性一般表示未感染过结核分枝杆菌，但感染初期、老年人、严重结核病患者或患有其他传染病，如麻疹、获得性免疫细胞功能低下，如艾滋病或使用免疫抑制剂致免疫功能受到抑制时...
