Đáp án:

\(mp(P) \perp mp(Q) \Leftrightarrow \vec{n_P} = (2, -2m, 4) \perp \vec{n_Q} = (m+3, -2, 5)  \)

\( \Leftrightarrow 2(m+3) + 4m + 20 = 0 \)  
\( \Leftrightarrow 6m + 26 = 0  \Leftrightarrow m = -\frac{13}{3} \approx -4.33 \Rightarrow \boxed{B} \)