What is true of a mixed-integer linear program?

A mixed-integer linear program (MILP) is characterized by its incorporation of both integer and continuous variables. This means that some of the variables in the model are required to take on integer values, while others can assume any value within a continuous range. This unique combination is particularly useful in various practical optimization problems where certain decisions are inherently discrete (such as the number of trucks to send on a delivery route) while others can vary continuously (like the amount of fuel used).

The presence of both types of variables allows for more flexibility in modeling complex situations. For instance, in scheduling, some tasks may be assigned to whole units (like workers or machines) while the duration of those tasks may be expressed in continuous time. This feature enables MILPs to effectively handle a wider range of real-world problems compared to standard linear programs that restrict all variables to continuous values.

The other options do not accurately represent the nature of MILPs. Some options incorrectly suggest that all variables must be integers or that the model lacks constraints, which is not true. Constraints are a fundamental part of any linear programming model, including mixed-integer programs, as they define the feasible region for the solution. Additionally, a focus solely on integer solutions does not capture the continuous variable aspect that