What term refers to the constraints placed on an objective function?

The term that refers to the constraints placed on an objective function is "subject to." In the context of optimization, especially in linear programming, an objective function is what you seek to maximize or minimize. The constraints define the limits within which the solution must lie. These constraints dictate the feasible region – the set of all possible solutions that satisfy the given conditions. Thus, the phrase "subject to" is commonly used to introduce these constraints, indicating that the solution must adhere to the conditions laid out.

For example, in a linear programming problem where you want to maximize profit while ensuring that resource usage does not exceed specific limits, the constraints that describe those limits would be introduced with the phrase "subject to." This terminology is standard in mathematical formulations involving optimization. The other terms do not correctly capture the essence of what constraints are or how they relate to the objective function.