First, determine the slope of the line. See image attached.
The slope of the line could be determine using the formula:


m = -1
Second, determine the equation of the line. The available information: m = -1 and one of the points that lies on the line is (x₁,y₁) = (0,-2).
Use this formula
y - y₁ = m(x - x₁)
y - (-2) = -1(x - 0)
y + 2 = -x
y + 2 = -x
x + y + 2 = 0
The answer is third option