【单选题】

As a project manager, you are aware that estimating schedule activity costs involves developing an approximation of the costs of the resources needed to complete each schedule activity. In approximating costs, the estimator considers the possible causes of variation of the cost estimates, including risks.Cost estimating includes identifying and considering various costing alternatives. For example, in most application areas, additional work during a design phase is widely held to have the potential for reducing the cost of the execution and product operations. The cost estimating process considers whether the expected savings can offset the cost of additional design work.Cost estimates are generally expressed in units of currency to facilitate comparisons both within and across projects.Cost estimates can also benefit from refinement during the course of the project to reflect on the additional detail available. For your project, which is in the initial phases, your team suggested a rough order of magnitude estimate—this could be in the range of ______ .

A、-75% to+125%
B．-50% to+100%
C．-25% to+50%
D．None of the above