QuestionLet $f$ be the function defined by $f(x)=\frac{3 x^{20}}{4 e^{x}+8 x^{20}}$ for $x>0$. Which of the following is a horizontal asymptote to the graph of $f$ ? (A) $y=0$
B $y=\frac{3}{8}$ (C) $y=\frac{3}{4}$ (D) There is no horizontal asymptote to the graph of $f$.