6. (2003 Shandong Province Competition Question) Let the sum of the first four terms of an arithmetic sequence be 26, and the sum of the last four terms be 110. The sum of all terms of this sequence is 187. Then, the number of terms in this sequence is ( ).
A. 11
B. 22
C. 8
D. 16
6. Choose A. Reason: Making full use of the given information, let the sequence have $n$ terms: $a_{1}, a_{2}, \cdots, a_{n}$, according to the problem we have
$$
\begin{array}{l}
a_{1}+a_{2}+a_{3}+a_{4}=26, \\
a_{n-3}+a_{n-2}+a_{n-1}+a_{n}=110 .
\end{array}
$$

Since the arithmetic sequence satisfies
$$
a_{1}+a_{n}=a_{1}+a_{n-1}=a_{3}+a_{n-2}=a_{4}+a_{n-3} \text {, }
$$

we have, $4\left(a_{1}+a_{n}\right)=26+110=136, a_{1}+a_{n}=34$.
$$
\text { Also, } \frac{n\left(a_{1}+a_{n}\right)}{2}=187 \text {, i.e., } \frac{n \times 34}{2}=187 \text {, thus } n=11 \text {. }
$$