Explanation
The schedule performance index (SPI) and the cost performance index (CPI) are earned value management (EVM) measures for project schedule and cost efficiency respectively. SPI and CPI are used to assess the magnitude (or amount) of variation from the established schedule and cost baselines1.
The SPI is calculated by dividing the earned value (EV) by the planned value (PV). The CPI is calculated by dividing the EV by the actual cost (AC). Both indexes have a target value of 1, which means the project is on track. An SPI or CPI less than 1 indicates that the project is behind schedule or over budget, respectively. An SPI or CPI greater than 1 indicates that the project is ahead of schedule or under budget, respectively2.
In this question, the project has an SPI of 0.75 and a CPI of 1.25, which means that the project is behind schedule but under budget. The project manager should report the project status to key stakeholders in a way that shows the project is under control and that corrective actions are being taken to address the schedule variance.
Option A is not the best answer because performing a detailed root cause analysis using pareto charts and fishbone diagrams may be too time-consuming and complex for a monthly status report. The project manager should focus on the key issues and actions, not the details of the analysis.
Option C is not the best answer because preparing a detailed presentation on earned value may be too technical and overwhelming for some stakeholders who are not familiar with EVM. The project manager should use simple and clear language to explain the project status and the implications of the EVM results.
Option D is not the best answer because reporting that the project is not tracking as expected but is still under control may not be convincing or reassuring for the stakeholders. The project manager should provide evidence and rationale for why the project is under control and what steps are being taken to improve the schedule performance.
Option B is the best answer because reporting that the project is behind schedule but that an additional experienced resource can be added to stay within schedule and maintain the budget is a realistic and proactive way to communicate the project status. The project manager acknowledges the schedule problem, proposes a feasible solution, and demonstrates confidence in the project's ability to meet the budget and the deadline. References:
1: PMBOK Guide, 7th edition, page 261
2: Schedule & Cost Performance Index, with Formulae & Examples (SPI/CPI)3