$2$

Consider a school with two periods during which

classes can be scheduled. For each class, there are

two variables. For example, for class $A,$ there are

variables $x_{A1}$ and $x_{A2}.$ Setting $x_{A2}=1$

represents scheduling class A during period $2.$

Select the Boolean expression that is true if and

only if class $A$ is scheduled during exactly one of

the two periods.

$(x_{A1}+x_{A2})(\frac{?}{\text{b}\text{a}\text{r}}(x_{A1}{x}_{A2}))$

$(x_{A1}{x}_{A2})(\frac{?}{\text{b}\text{a}\text{r}}(x_{A1})\frac{+}{b}ar(x_{A2}))$

$(x_{A1}+x_{A2})(\frac{?}{\text{b}\text{a}\text{r}}\frac{x_{A1}}{b}ar(x_{A2}))$

$(x_{A1}{x}_{A2})(\frac{?}{\text{b}\text{a}\text{r}}(x_{A1}+x_{A2}))$