Answer:
C. y = -2x - 1
Explanation:
y = mx + b
The slope is going down so that means that the m will be negative.
We are left with two choices:
y = -2x - 1
y = -2x + 1
Check the graph again to find what point does the line intersect the vertical line (y-axis). That hits in (0, -1) or -1.
So the only answer applicable is option C.