Ok so in order for the equation to be perpendicular, the slope have to be opposite of each other.
The original equation had -2 as the slope. The opposite of -2 is 1/2.
When the number is negative, the opposite of it is positive.
And in order for them to be completely opposite, you have to flip the number. So 2 turned into 1/2, since the denominator of 2 is 1.
And so since the opposite slope is 1/2, C is the correct answer.