The Main Disadvantage of Introducing Constraints into a Linear Program

Multiple Choice

The main disadvantage of introducing constraints into a linear program that enforce some or all of the decision variables to be either integer or binary is that:

A) the programs may take longer to solve.
B) the solutions will no longer be optimal.
C) Excel can no longer be used to solve the program.
D) the constraints are difficult to formulate.
E) we cannot have "yes-or-no" decisions in the linear program.