Which slope-intercept equation describes the line?

The answer would be C. y=-x-2 because you have a negative 1 slope so that would be -x(x counts as one). Then, the intercept is -2 which will give you at the end -2.

Well, you must think of the Slope-Intercept formula first, and what the variables mean.
y = mx + b
M = Slope
B = Y-intercept

Since we know that the line has a slope of -1 and a Y-intercept of -2 we can substitute accordingly
M/Slope = -1
B/Y-intercept = -2
y = -x - 2 should be your answer