Question $1.$

Consider two decisions A and $B$ represented by two binary decision variables $xA$ and $xB,$ each of which takes $1$ if the decision is made to choose it$,$ and $0$ otherwise. Select an appropriate expression from $1-8$ for the constraint in each question.

$xA+xB=0$

$xA-xB=0$

$xA+xB0$

$xA-xB0$

$xA+xB=1$

$xA+xB1$

$xA+xB1$

$(8)xA+xB=2$