6. An increasing sequence of positive integers $\left\{a_{n}\right\}$ has the following property: for any $n \in \mathbf{N}_{+}$, it holds that $a_{n+2}=a_{n+1}+a_{n}$, and $a_{7}=120, a_{8}$ is ( ).
A. Uncertain
B. Equal to 194
C. Equal to 200
D. Equal to 216
6. B,

From the recursive formula, we get $a_{7}=5 a_{1}+8 a_{2}=120$, from which we can find $a_{1}=8, a_{2}=10$, thus $a_{8}=8 a_{1}+13 a_{2}=$ 194.