[单选题]
A thin metal plate o lpuwbcti, x8l.+o1m9 f mass m is held at an absolute temperature T, in d8pp thd r:i/ckdg*:+an enclosure o:i:8gp/*tdd+ rhk dpc f 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. $\frac{2σA(T^4-T_s^4)Δt}{m(Δt}$