Given $x > 0$,the value of $f(x)=-3\cos \sqrt{3+x+x^2}$ lie in the interval _________

$\begin{array}{1 1}(A)\;-3,3&(B)\;-2,2\\(C)\;-1,1&(D)\;-4,4\end{array}$

$\cos \theta$ lies in the interval [-1,1]
$\therefore -3\cos\sqrt{3+x+x^2}$ lies in the interval [-3,3]
Hence (A) is the correct answer.