Answer
(A)
Work Step by Step
A line in slope-intercept form has the equation:
$y=mx+b$ ($m=slope$, $b=y-intercept$)
We convert the line equation to slope-intercept form:
$x+3y=-3$
$3y=-3-x$
$y=(-3-x)/3$
$y=-1-\frac{1}{3}x$
$y=-\frac{1}{3}x-1$
So the line has a $y$-intercept of -1 and a negative slope. Only (A) matches these properties.