已知数列\(\{a\)\({\,\!}_{n}\) \(\}\)是首项为\(a\)，公差为\(1\)的等差数列，数列\(\{b\)\({\,\!}_{n}\) \(\}\)满足\(b\)\({\,\!}_{n}\) \(=\)\( \dfrac{1+a_{n}}{a_{n}}\) \(.\)若对任意的\(n∈N\)\({\,\!}^{*}\) ，都有\(b\)\({\,\!}_{n}\) \(\geqslant b\)\({\,\!}_{8}\) 成立，则实数\(a\)的取值范围是\((\) \()\)
A. \((-8,-7)\)
B. \([-8,-7)\)
C. \((-8,-7]\) D. \([-8,-7]\)
