Idea: Expand the acronym and read its intent.
COCOMO means Constructive Cost Model, so its target quantity is cost. It maps project size to effort:
\[ E = a \,(\text{KLOC})^{b} \]
and effort maps to money and staffing. Duration is a secondary output, and management or validation are not what the model computes. The core use is cost estimation.
\[\boxed{\text{Option B: Estimating software development costs}}\]