In a binary integer programming problem when a decision variable x $=1$ corresponds to a $$yes$$ decision and x $=0$ to a $$no$$ decision, which of the following formulates the condition that $3$ alternatives $($represented by decision variables x$1,$ x$2$ and x$3)$ are mutually exclusive? Group of answer choices x$1+$ x$2+$ x$3>=1$ x$1+$ x$2+$ x$3=1$ x$1+$ x$2+$ x$3<=2$ x$1+$ x$2+$ x$3<=1$