12. For the quadratic function $f ( x ) = a x ^ { 2 } + b x + c$ (where $a$ is a non-zero constant), four students each give a conclusion. Exactly one conclusion is wrong. The wrong conclusion is\\
A. $-1$ is a zero of $f ( x )$\\
B. $1$ is an extremum point of $f ( x )$\\
C. $3$ is an extremum value of $f ( x )$\\
D. The point $( 2,8 )$ lies on the curve $y = f ( x )$
\section*{II. Fill in the Blanks}