Question

what is the equation of the horizontal line that passes through the point (-2, -1)?

Answer 1

A horizontal line has no slope. It simply has a Y value.
*Your ordered pair has a Y value, too. Hmmmm*

Answer 2

is it ; y=-1, y= -2, x = -2, or x = -1

Answer 3

It is
y=-1

Reason: (-2,-1) demands that you move first, left by two units and second, down by one unit. So you are at y=-1.

Any x=(anything) will give you a vertical line.