[单选题]
A thin metal plate ofvtkg 0.4p yx8d4xedz( mass m is h8cc kl q85dh-qeld at an absolute temperature T, in an enclosurhqd c8c-5 8lqke of temperature $T_s$
A. $\frac{σAT^4Δt}{m(Δt}$
B. $\frac{σA(T^4-T_s^4)Δt}{m(Δt}$
C. $\frac{2σAT^4Δt}{m(Δt}$
D. $\frac{2σA(T^4-T_s^4)Δt}{m(Δt}$