Chọn phương án C.

\(\begin{aligned}
&\lim\dfrac{3n+\sqrt{n^2+n-5}}{-2n}\\
=&\lim\dfrac{3n+\sqrt{n^2\left(1+\dfrac{1}{n}-\dfrac{5}{n^2}\right)}}{-2n}\\
=&\lim\dfrac{3n+n\sqrt{1+\dfrac{1}{n}-\dfrac{5}{n^2}}}{-2n}\\
=&\lim\dfrac{3+\sqrt{1+\dfrac{1}{n}-\dfrac{5}{n^2}}}{-2}\\
=&\dfrac{3+\sqrt{1+0-0}}{-2}=-2.
\end{aligned}\)