If $\lim\limits_{x\to \infty}\bigg[\large\frac{x^2+x+1}{x+1}$$-ax-b\bigg]=4$ then

Question

$\begin{array}{1 1}(a)\;a=1,b=4&(b)\;a=1,b=-4\\(c)\;a=2,b=-3&(d)\;a=2,b=3\end{array}$