The curve disturbed parametrically by $x=t^2+t+1\;y=t^2-t+1$ represents

Question

$\begin{array}{1 1}(A)\;\text{a pair of straight line} \\(B)\;\text{an ellipse} \\ (C)\;\text{a parabola} \\(D)\;\text{a hyperbola} \end{array}$