A

\(8,lim\dfrac{3n^2+n-2}{4n^3+n+1}\)

\(=lim\dfrac{\dfrac{3n^2}{n^3}+\dfrac{n}{n^3}-\dfrac{2}{n^3}}{\dfrac{4n^3}{n^3}+\dfrac{n}{n^3}+\dfrac{1}{n^3}}\)

\(=lim\dfrac{\dfrac{3}{n}+\dfrac{1}{n^2}-\dfrac{2}{n^3}}{4+\dfrac{1}{n^2}+\dfrac{1}{n^3}}\)

\(=\dfrac{0}{4}\)

\(=0\)

\(9,lim4n^3+2n-5\)

\(=lim\left(\dfrac{4n^3}{n^3}+\dfrac{2n}{n^3}-\dfrac{5}{n^3}\right)\)

\(=lim\left(4+\dfrac{2}{n^2}-\dfrac{5}{n^3}\right)\)

\(=4\)

\(10,lim\left(n^2-n+1\right)\)

\(=lim\left(\dfrac{n^2}{n^2}-\dfrac{n}{n^2}+\dfrac{1}{n^2}\right)\)

\(=lim\left(1-\dfrac{1}{n}+\dfrac{1}{n^2}\right)\)

\(=1\)

\(11,lim\left(-2n^3+n+5\right)\)

\(=lim\left(-\dfrac{2n^3}{n^3}+\dfrac{n}{n^3}+\dfrac{5}{n^3}\right)\)

\(=lim\left(-2+\dfrac{1}{n^2}+\dfrac{5}{n^3}\right)\)

\(=-2\)

\(12,lim\left(-3n^4+n+7\right)\)

\(=lim\left(-\dfrac{3n^4}{n^4}+\dfrac{n}{n^4}+\dfrac{7}{n^4}\right)\)

\(=lim\left(-3+\dfrac{1}{n^3}+\dfrac{7}{n^4}\right)\)

\(=-3\)

A