In the right triangular prism $ABC - A_1B_1C_1$, let $D$ be the midpoint of $BC$. Then A. $AD \perp A_1C$ B. $BC \perp$ plane $AA_1D$ C. $AD \parallel A_1B_1$ D. $CC_1 \parallel$ plane $AA_1D$
In the right triangular prism $ABC - A_1B_1C_1$, let $D$ be the midpoint of $BC$. Then\\
A. $AD \perp A_1C$\\
B. $BC \perp$ plane $AA_1D$\\
C. $AD \parallel A_1B_1$\\
D. $CC_1 \parallel$ plane $AA_1D$