Question

Choose the equation of the horizontal line that passes through the point (1, -5)

Answer 1

Horizontal lines have a slope of 0. So, using point slope form:
(y-y₁) = m(x-x₁)
y-(-5) = 0(x-1)
y+5 = 0
y = -5

Answer 2

horizontal line passing through the point (1, -5)...

horizontal line means y = something
the y value of the point is -5, that's the something

thus y = -5.

Answer 3

something has to be a constant