You should verify that enforcing consistency for $($A

$->$

$->$ C$),($A

$->$

$->$ D$),($B

$->$

$->$ A$),($B

$->$

$->$ C$),($B

$->$

$->$ D$),$ and $($C

$->$

$->$ A$)$ do not change the domains of any variables. After enforcing these arcs, the list of arcs on the queue is:

$($A

$->$

$->$ B$),($A

$->$

$->$ C$),($A

$->$

$->$ D$),($B

$->$

$->$ A$),($B

$->$

$->$ C$),($B

$->$

$->$ D$),($C

$->$

$->$ A$),($C

$->$

$->$ B$),($C

$->$

$->$ D$),($D

$->$

$->$ A$),($D

$->$

$->$ B$),($D

$->$

$->$ C$)$

The next arc to check is C

$->$

$->$ B$.$

Which variable's domain changes?

Choice $1$ of $4$: A

Choice $2$ of $4$: B

Choice $3$ of $4$: C

Choice $4$ of $4$: D

Grading comment:

What values remain in the domain of that variable? $($Select the values that remain; do not select the values that have been eliminated.$)$