Cho hàm số \(f\left( x \right) = \sqrt {x + 1} - \sqrt {x + 2} \). Mệnh đề đúng là A. \(\mathop {\lim }\limits_{x \to + \infty } f\left( x \right) = - \infty \). B. \(\mathop {\lim }\limits_{x \to + \infty } f\left( x \right) = 0\). C. \(\mathop {\lim }\limits_{x \to + \infty } f\left( x \right) = - 1\). D. \(\mathop {\lim }\limits_{x \to + \infty } f\left( x \right) = - \frac{1}{2}\).