单项选择题 In approximating costs, the estimator considers the possible causes of variation of the cost estimates, including（） .

单项选择题 On some projects, especially ones of smaller scope, activity sequencing, activity resource estimating, activity duration estimating, and （） are so tightly linked that they are viewed as a single process that can be performed by a person over a relatively short period of time.

单项选择题 Project （） Management includes the processes required to ensure that the project includes all the work required, and only the work required, to complete the project successfully.