2. Let the real number $x$ satisfy $x^{3}=x+1$. If $x^{7}=a x^{2}+b x+c$, then the value of $a+b+c$ is ( ).
(A) 3
(B) 4
(C) 5
(D)6
2. C.
$$
\begin{array}{l}
x^{7}=x(x+1)^{2}=x^{3}+2 x^{2}+x=2 x^{2}+2 x+1 \\
\Rightarrow a+b+c=5 .
\end{array}
$$