All of the offered choices agree that the multiplier of the exponential factor is 5. When x=1, the exponential factor must have a value of 2/5 in order to make the function value be 2 at that point.
That is, ...
f(1) = 5(2/5)^1 = 5(2/5) = 2
You can get there either by using x=1 in each of the offered answer choices, or by observing that the ratio between f(1) and f(0) is 2/5.
