\( \mathop { \lim } \limits_{x \to - \infty } \dfrac{1}{{ \sqrt {{x^2} + x + 1} - x}} \)
A.\(\mathop {\lim }\limits_{x \to  - \infty } \dfrac{1}{{\sqrt {{x^2} + x + 1}  - x}} = + \infty\).
B.\(\mathop {\lim }\limits_{x \to  - \infty } \dfrac{1}{{\sqrt {{x^2} + x + 1}  - x}} = - \infty\).
C.\(\mathop {\lim }\limits_{x \to  - \infty } \dfrac{1}{{\sqrt {{x^2} + x + 1}  - x}} = - \dfrac{1}{4}\).
D.\(\mathop {\lim }\limits_{x \to  - \infty } \dfrac{1}{{\sqrt {{x^2} + x + 1}  - x}} = 0\).

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