Phương pháp giải:

Sử dụng định lí: $\left\{ \begin{array}{l}d \bot a\\d \bot b\\a \cap b \subset \left( P \right)\end{array} \right. \Rightarrow d \bot \left( P \right)$, $\left\{ \begin{array}{l}d \bot \left( P \right)\\a \subset \left( P \right)\end{array} \right. \Rightarrow d \bot a$.

Lời giải chi tiết:

+ $\left\{ \begin{array}{l}CD \bot AD\\CD \bot SA\end{array} \right. \Rightarrow CD \bot \left( {SAD} \right)$.

+ $\left\{ \begin{array}{l}CD \bot \left( {SAD} \right)\\AK \subset \left( {SAD} \right)\end{array} \right. \Rightarrow CD \bot AK$.

+ $\left\{ \begin{array}{l}AK \bot SD\,\,\left( {gt} \right)\\AK \bot CD\,\,\left( {cmt} \right)\end{array} \right. \Rightarrow AK \bot \left( {SCD} \right)$.

Chọn B.