Alright, I don't know what your choices are, but here's my input:
For a line to be perpendicular to another line, the slope needs to be the opposite reciprocal of the slope of the given line. Now, by opposite, I mean if your slope is positive, this one needs to be negative (or vice versa). For reciprocal, I mean flip the fraction over. In this case, we have a slope of 2, so its opposite is -2 & the reciprocal is -1/2. So, whatever line has a slope of -1/2 is your answer.
Hope this helps!