[单选题]
A thin metal plate o3s7(a,*fy1d 9(aeo u7h m;i b pzragjtxs rk b ,i7,-kigmda74f mass m is held at an absolute temperature T, in an enclosure of tegx4 k,i kb7 i7-mrasd,mperature $T_s$
A. $\frac{σAT^4Δt}{m(Δt}$
B. $\frac{σA(T^4-T_s^4)Δt}{m(Δt}$
C. $\frac{2σAT^4Δt}{m(Δt}$
D. $\frac{2σA(T^4-T_s^4)Δt}{m(Δt}$