Let f(x)=8^x.

Which function represents a transformation of f(x) by a vertical stretch with factor 2??

A- g(x)=1/2*8^x

B- g(x)=8^2x

C- g(x)=2*8^x

D- g(x)=8 1/2^x

Please help and give reasoning with your answer. I’m very unsure.