Đáp án đúng: D $\begin{gathered} (1)\,\,C = C - C - C \hfill \\ (2)\,C - C = C - C\,\,(co\,đphh) \hfill \\ (3)\,\,C = C = C - C \hfill \\ (4)\,\,C = C - C = C \hfill \\ (5)\,\,C \equiv C - C - C \hfill \\ (6)\,\,C - C \equiv C - C \hfill \\ (7)\,\,C \equiv C - C \equiv C \hfill \\ (8)\,\,C \equiv C - C = C \hfill \\ \end{gathered} $