you want to get an answer which results in y = ax. Since you are not given an a to work with a = 1.
so you want something that will eventually work out to y = x
Therefore c and d can't work. You will get something that works out to y = ksqrt(x)
The second best answer is B but that minus sign gets in the way.
1/y = 1/x Cross multiply
x = y which is exactly what you want.
A<<<< answer.