Line $l\_1$ has equation $2x-y=3$ and goes through $A=(1,-1)$. Line $l\_2$ has equation $y=1$ and meets line $l\_1$ at point $B$. Line $l\_3$ has negative slope, goes through point $A$, and meets $l\_2$ at point $C$. The area of $\triangle A B C$ is $3$. What is the slope of $l\_3$? (Adapted From 2013 AMC 12B Problems, Question \#8) 
选项为:A:$$-\frac23$$  B:$$-\frac34$$  C:$$-1$$  D:$$-\frac43$$  E:$$-2$$  请回答其中一个选项.