The graph of the line y = 4 is a
a) vertical line with a slope of zero.
b) horizontal line with a slope of zero.
c) vertical line with an undefined slope.
d) horizontal line with an undefined slope.

 horizontal line with a slope of zero.

Step-by-step explanation:

The graph of the line y = 4 is a

when we graph y=4, we get a line at y=4

the graph of y=some number gives us a horizontal line

the graph of x= some number gives us a vertical line at that number

y=4, is the graph of a horizontal line at 4. for all horizontal lines the slope is 0

for all vertical lines the slope is undefined

for y=4 , the slope of the line is zero

 horizontal line with a slope of zero.

is only a line? i think so