In the Basic COCOMO (Constructive Cost Model) estimation model, which factor is the primary input used to estimate software development effort?

The Basic COCOMO model estimates software development effort primarily as a function of the project's estimated size, measured in thousands of lines of code (KLOC), using an effort equation of the general form Effort = a × (KLOC)^b, where the constants a and b vary depending on the project's development mode (organic, semi-detached, or embedded). This distinguishes COCOMO's sizing approach from Function Point Analysis (option A), which is an entirely separate estimation technique based on counting functional requirements rather than lines of code.