若当前世界上主要产油国的石油产量减少，则国际市场上汽油的价格( )。

A．升高

B．不变

C．可能不变也可能变化

D．降低

（）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:（）, the initiation of the successor activity, depends upon the completion of the predecessor activity.

（）, the initiation of the successor activity, depends upon the initiation of the predecessor activity.

（）is a method of constructing a project schedule network diagram that uses boxes or rectangles.

A．PDM

B．CPM

C．PERT

D．AOA