Assume that we are using $0-1$ integer programming model to solve a capital budgeting problen and $x_j=1$ if project $j$ is selected and $x_j=0,$ otherwise.

The constraint $)(1$ means that out of the projects must be selected.

A$)$ exactly $2,4$

B$)$ exactly $1,4$

C$)$ at least $1,4$

D$)$ at most $1,4$