Concept:
The slope of tangent is obtained using differentiation.
The slope of normal is the negative reciprocal of tangent slope.
Step 1: Differentiate the curve.
Given,
\[
y=\ln x
\]
Differentiating with respect to \(x\),
\[
\frac{dy}{dx}=\frac{1}{x}
\]
Step 2: Find slope of tangent at \(x=1\).
At the point \(P(1,0)\),
\[
m_t=\frac{1}{1}=1
\]
Thus tangent slope is:
\[
m_t=1
\]
Step 3: Find slope of normal.
Slope of normal is negative reciprocal of tangent slope.
\[
m_n=-1
\]
Step 4: Use point-slope form.
Equation of line:
\[
y-y_1=m(x-x_1)
\]
Substituting point \((1,0)\) and slope \(-1\),
\[
y-0=-1(x-1)
\]
\[
y=-x+1
\]
Rearranging,
\[
x+y=1
\]
Step 5: Conclusion.
Hence the equation of normal is:
\[
\boxed{x+y=1}
\]
Therefore, the correct answer is:
\[
\boxed{(D)}
\]