The set of all values of $a$ for which $\displaystyle \lim_{x \to a} ([x - 5] - [2x + 2]) = 0$, where $[\alpha]$ denotes the greatest integer less than or equal to $\alpha$ is equal to:
\( [-7.5,\,-6.5] \)
\( [-7.5,\,-6.5) \)
\( (-7.5,\,-6.5) \)