在留设保护煤柱时，应注意什么？

Resource calendars affect a specific resource or category of resources. They reflect how some resources work only during normal business hours, while others work three full shifts, or a project team member might be unavailable, such as on vacation or in a training program, or a labor contract can limit certain workers to certain days of the week. Resource calendars are valuable inputs for ______ .

A．developing an approximation of the costs of the resources needed to complete each schedule activity

B．aggregating the estimated costs of individual schedule activities or work packages to establish a total cost baseline for project performance

C．searching the cause of positive and negative variances as part of integrated change control process

D．assuring that potential cost overruns do not exceed the authorized funding periodically and in total for the project