The Cost Estimation technique that involves expert judgments and consensus is…

Software cost-estimation techniques fall into two broad families: algorithmic (model-based) techniques that compute effort from measurable parameters via a formula, and non-algorithmic (expert-judgment) techniques that rely on the experience and consensus of human experts. The Delphi Method is the classic expert-judgment technique: a panel of experts independently estimates cost, a coordinator anonymously collates and shares the results, and the panel repeats the round until the estimates converge to a group consensus.

The question describes a technique built on expert judgments and consensus, which is precisely the Delphi Method's iterative, anonymous, consensus-building process.

Contrast with the other options:

• COCOMO (Constructive Cost Model): an algorithmic model that computes effort directly from an estimated program size (KLOC) and a set of cost-driver multipliers, a formula, not a panel of experts reaching consensus.

• Waterfall Model: a sequential software development life-cycle model describing the order of development phases (requirements, design, implementation, testing), not a cost-estimation technique at all.

• Prototype Model: an iterative development life-cycle model built around building and refining prototypes with user feedback, again a development process model, not an estimation technique.