$\textit{Answer:}$

$\text{1.}$

$\textit{a,}$ Nhóm hợp chất hữu cơ:

- $\textit{C6H6}$

- $\textit{C6H12O6}$

- $\textit{C2H4}$

- $\textit{CH3CL}$

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