1. Given the sequence $\left\{a_{n}\right\}$ with the sum of the first $n$ terms $S_{n}=n^{2}-1\left(n \in \mathbf{N}_{+}\right)$, then $a_{1}+a_{3}+a_{5}+a_{7}+a_{9}=$
A. 40
B. 44
C. 45
D. 49
Solve $a_{1}=0, n \geqslant 2$ when $a_{n}=2 n-1$. Then $a_{1}+a_{3}+a_{5}+a_{7}+a_{9}=0+5+9+13+17=44$, so the answer is $B$.