$\text{A.}$ 若 $\alpha \perp \beta, \alpha \perp \gamma, \beta \cap \gamma=c$ ，则 $c \perp \alpha$
$\text{B.}$ 若 $\alpha \perp \beta, \alpha \perp \gamma, a \subset \alpha, a \perp \beta, c \subset \gamma$ ，则 $a \perp c$
$\text{C.}$ 若 $a / / \beta / / \gamma, c / / \gamma, a \subset \alpha, b \subset \beta$ ，则 $a / / b / / c$
$\text{D.}$ 若 $a \perp \alpha, b \perp \beta, c \perp \gamma, a / / b / / c$ ，则 $\alpha / / \beta / / \gamma$
$\text{E.}$
$\text{F.}$