Your line would have to be horizontal. A vertical line yields an undefined slope.
Slope is rise over run. For a horizontal line you would have 0 rise and X amount of run or 0/x. 0 divided by anything = 0
For a vertical line, you would have the opposite, X rise and 0 run or x/0. You cannot divide by 0. It is impossible.
Therefore, your answer is the second option.
