[warut]

5(B) $$\sum_{n=1}^{100} \frac{n^2-n+1} {n^4-n^3+n^2-n+1} < \sum_{n=1}^\infty \frac{1}{n^2+ \displaystyle{ \frac{1-n}{n^2-n+1} }} < 1+ \sum_{n=2}^\infty \frac{1}{n^2-1} = 1.75 < 1.99 $$