1. Given $x_{1}=6, x_{2}=4, x_{n+2}=\frac{x_{n+1}^{2}-4}{x_{n}}$, the sequence $\left\{x_{n}\right\}$ satisfies ( ).
A. Only has a finite number of terms, and satisfies $x_{n+2}=2 x_{n+1}-x_{n}$
B. Has an infinite number of terms, and satisfies $x_{n+2}=2 x_{n+1}-x_{n}$
C. Only has a finite number of terms, and satisfies $x_{n+2} \neq 2 x_{n+1}-x_{n}$
D. Has an infinite number of terms, and satisfies $x_{n+2}=2 x_{n+1}-x_{n}$
1. A,

When $x_{1}=6, x_{2}=4, x_{3}=2, x_{4}=0, x_{5}=-2, n=6$, $x_{6}$ does not make sense, does not exist, and $x_{5}-$ $x_{4}=x_{4}-x_{3}=x_{3}-x_{2}=x_{2}-x_{1}=-2$ always holds.