Let \( [ x ] \) denote the greatest integer less than or equal to \( x \). Then the domain of \( f(x)=\sec^{-1}(2[ x ] + 1) \) is:
\( (-\infty,-1)\cup[1,\infty) \)
\( (-\infty,-1)\cup[0,\infty) \)
\( (-\infty,\infty)-\{0\} \)
\( (-\infty,\infty) \)