[单选题]
A thin metal plate of h/dd:yh zl0- umass m is kwnf2v: y5h7y. 7ubo3)o,pr uf byq1 pheld at an absolute temperature T, in an enclosure of trbbh:o.uqw51nfy2f kyv)uy3o7p,p 7emperature $T_s$
A. $\frac{σAT^4Δt}{m(Δt}$
B. $\frac{σA(T^4-T_s^4)Δt}{m(Δt}$
C. $\frac{2σAT^4Δt}{m(Δt}$
D. $\frac{2σA(T^4-T_s^4)Δt}{m(Δt}$