کدام گزینه برای شکل مقابل مناسب است؟

1 )
$\left. \begin{gathered}
a \bot c \hfill \\
b \bot c \hfill \\
\end{gathered} \right\} \to a \bot b$
2 )
$\left. \begin{align} & a\bot c \\ & a\bot b \\ \end{align} \right\}\to a\parallel b$
3 )
$\left. \begin{align} & a\bot c \\ & b\parallel c \\ \end{align} \right\}\to a\bot b$
$\left. \begin{align} & a\parallel b \\ & c\bot a \\ \end{align} \right\}\to c\bot b$