The graph of logarithm function $f(x)=\ln x$ (gray) and logarithm function $g(x)$ (black) is drawn below. $g(x)$ is a transformation of $f(x)$.

What sort of transformation is $g(x)$ of $f(x)$ ?
Choices:
A:Vertical dilation
B:Vertical translation
C:Reflection
D:Horizontal translation
Please directly answer the question and provide the correct option letter, e.g., A, B, C, D.
Question: The graph of logarithm function $f(x)=\ln x$ (gray) and logarithm function $g(x)$ (black) is drawn below. $g(x)$ is a transformation of $f(x)$.

What sort of transformation is $g(x)$ of $f(x)$ ?
Choices:
A:Vertical dilation
B:Vertical translation
C:Reflection
D:Horizontal translation
Please first conduct reasoning, and then answer the question and provide the correct option letter, e.g., A, B, C, D, at the end.
Question: The graph of logarithm function $f(x)=\ln x$ (gray) and logarithm function $g(x)$ (black) is drawn below. $g(x)$ is a transformation of $f(x)$.

What sort of transformation is $g(x)$ of $f(x)$ ?
Choices:
A:Vertical dilation
B:Vertical translation
C:Reflection
D:Horizontal translation