The function is a natural logarithm. While the logarithmic function \( \ln(x) \) has a range of \( (-\infty, \infty) \), the argument of this logarithm is a ratio of two terms, which constrains the function's range based on the values of \( x \). Analysis of the limits and function behavior indicates the range of \( f(x) \) is \( (0, 1] \).