A metal piece is heated up to T K; the temperature of the surrounding is t K. The heat loss to the surrounding due to radiation is proportional to:

• A

  ${\left(\mathrm{T}-\mathrm{t}\right)}^4$

• B

  ${\mathrm{T}}^4-{\mathrm{t}}^4$

• C

  ${\left(\mathrm{T}-\mathrm{t}\right)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$4$}\right.}$

• D

  ${\mathrm{T}}^2-{\mathrm{t}}^2$