Concept:
Political boundaries are created by humans to define territorial limits. Although they are primarily political, they also perform economic, administrative, strategic, cultural, and social functions. Therefore, they are not purely political in origin and function.
Step 1: Examine each statement.
\[
\begin{aligned}
A. &\ \text{Incorrect. Boundaries serve many functions besides political ones.}
B. &\ \text{Correct. Boundaries often reflect centrifugal forces that separate regions.}
C. &\ \text{Correct. The eastern India--China boundary is known as the McMahon Line.}
D. &\ \text{Correct. Political boundaries are selected and demarcated by humans.}
\end{aligned}
\]
Step 2: Identify the incorrect statement.
\[
\boxed{\text{Statement A}}
\]
Hence,
\[
\boxed{\text{(A)}}
\]