Answer
B
Work Step by Step
The basic function for the given graphs is $y=3^x$.
(1) If the function has a horizontal asymptote of $y=a$ and is below the asymptote, it will have the form of: $y=a-3^b$.
(2) If the function has a horizontal asymptote of $y=a$ and is above the asymptote, it will have the form of: $y=a+3^b$.
(3) The graph of $y=f(x-h)$ involves a horizontal shift of $|h|$ units (to the right when $h \gt 0$, to the left when $h\lt0$) of the parent function $f(x)$.
(4) If the graph is increasing, the exponent of $3$ is positive, if it is decreasing, it is negative.
The graph in the picture has a horizontal asymptote of $x=0$, is positive (above the horizontal asymptote) and decreasing.
All these are true for B hence it is B ($y=3^{-x})$.