A. f(x) = 3*(1/2)^x
We know that, a function can be stretched or shrinked both horizontally and vertically.
Now, according to our question we are required to look at the vertical stretch of an exponential function.
The general form for a vertical stretch of a function f(x) is k*f(x) where k>1.
So, we compare this form with the options provided.
We see that in option A the exponential function is multiplied by 3 and so the function will be stretched vertically.
Hence, option A is correct.
Selection A seems appropriate.
It is of the form k*f(x), where f(x) is an exponential function and k > 1.