Final answer:
Estimating and forecasting the Portfolio Backlog are ongoing and collaborative processes involving multiple stakeholders, not limited to the portfolio manager or only epics. It is vital for effective investment decisions and prioritization within Agile frameworks.
Step-by-step explanation:
The true statement about estimating and forecasting the Portfolio Backlog is that it is c) An ongoing and collaborative effort.
In the context of Agile frameworks such as SAFe, estimating and forecasting involve the continuous participation of various stakeholders including the portfolio managers, Enterprise Architects, Product Owners, and Business Owners. The process is not limited to any one individual or one-time event.
Moreover, while epics are significant, all items in the portfolio backlog, including initiatives and capabilities, should be estimated and forecasted to effectively guide investment decisions and prioritize value delivery.