Answer:
y = 1
Step-by-step explanation:
Slope is written in the form y=mx+b. Where m is the slope and b is the y-intercept.
When there isn't a slope, as in the line is flat and it isn't moving up or down, you wouldn't write anything for it. You would just write y equals the y-intercept (y = b).
Likewise, if the y-intercept is at (0,0), then you'd only write y equals the slope (y = mx).
Hopefully this makes sense :)
Btw, I also answered in the main comments earlier, so you can check that out as well.