5. Let $a, b, c$ be three different lines, and $\alpha, \beta, \gamma$ be two different planes. Which of the following propositions is true? ( ).
(A) If $\alpha \perp \gamma, \beta \perp \gamma$, then $\alpha / / \beta$
(B) If $a \perp b, b \perp c$, then $a / / c$ or $a \perp c$
(C) If $a \subset \alpha, b, c \subset \beta, a \perp b, a \perp c$, then $\alpha \perp \beta$
(D) If $a \perp \alpha, b \subset \beta, a / / b$, then $\alpha \perp \beta$
5. (D).
(A) $\alpha$ and $\beta$ can intersect, so (A) is incorrect; (B) $a$ and $c$ can be skew and not perpendicular, so (B) is incorrect; (C) when $a \perp b, a \perp c$, $\alpha$ and $\beta$ can be parallel, (C) is incorrect.