6. As shown in the figure, $M$ is the midpoint of arc $C A B$, line segment $M P$ is perpendicular to chord $A B$ at $P$, and $A C=1 \mathrm{~cm}, P B=96 \mathrm{~cm}$, the length of $P A$ is:
(A) $77 \mathrm{~cm}$
(B) $96 \mathrm{~cm}$
(C) $67 \mathrm{~cm}$
(D) $115 \mathrm{~cm}$
6. A.

On $BP$, intercept $BD=AC$.
$$
\begin{array}{l}
\because \overparen{M C}=\widehat{M B}, \\
\therefore M B=M C, \\
\text { and } \angle B=\angle C,
\end{array}
$$
$\therefore \triangle M B D \cong \triangle M C A$. $C$
Thus, $M A=M D$.
Also, $M P \perp A D$,
Therefore, $A P=P D$.
So, $P A=P D=96-19=7(\mathrm{~cm})$.