극한 $\displaystyle \lim _ {x \rightarrow 0} {\frac{\sin \left (\sqrt {x^2 +4} -2 \right)} {\cos \left (xe^x \right) -1}}$ 를 구하면?

• ①$\displaystyle \frac{1} {4}$
• ②$\displaystyle - \frac{1} {4}$
• ③$\displaystyle \frac{1} {2}$
• ④$\displaystyle - \frac{1} {2}$
• ⑤$1$