2. In a real geometric sequence, the sum of the first two terms is 7, and the sum of the first six terms is 91. Then the sum of the first four terms is
A. 49
B. 35
C. 32
D. 28
2. D Let the first term and common ratio of the geometric sequence be $a$ and $q$, respectively. Thus, $\left\{\begin{array}{l}a + a q = 7 \\ \frac{a\left(q^{6}-1\right)}{q-1}=91\end{array}\right.$, dividing the two equations yields $\frac{q^{6}-1}{q^{2}-1}=$ 13, which simplifies to $\left(q^{2}+4\right)\left(q^{2}-3\right)=0$, hence $q^{2}=3$.
Therefore, $q + a q + a q^{2} + a q^{3}=(a + a q)\left(1 + q^{2}\right)=28$.