Question $14(1$ point$)$

In a BIP problem with $2$ mutually exclusive alternatives, x$1$ and x$2,$ the following constraint needs to be added to the formulation:

Question $14$ options:

x$1$ x$2=1.$

x$1$ x$2<=1.$

x$1+$ x$2>=1.$

x$1+$ x$2<=1.$