Determine which, if any, of these functions might be used as a model for the data in the scatterplot.
a) Quadratic$, f(x)=a x^{2}+b x+c$
b) Polynomial, not quadratic
c) Exponential, $f(x)=a b^{x},$ or $P_{0} e^{k x}, k>0$
d) Exponential, $f(x)=a b^{-x},$ or $P_{0} e^{-b x}, k>0$
e) Logarithmic, $f(x)=a+b \ln x$
f) Logistic$, f(x)=\frac{a}{1+b e^{-k x}}$