A small pond of depth 0.5 m deep is exposed to a cold winter with outside temperature of 263 K. Thermal conductivity of ice is $$K = 2.2\ \text{Wm}^{-1}\text{K}^{-1}$$, latent heat $$L = 3.4 \times 10^5\ \text{Jkg}^{-1}$$ and density $$\rho = 0.9 \times 10^3\ \text{kgm}^{-3}$$. Take the temperature of the pond to be 273 K. The time taken for the whole pond to freeze is about

A

20 days

B

25 days

C

30 days

D

35 days