[单选题]
An ideal gas piston oq r 1.cmvzosv,7 kj.-uf ys(npb(/csqq + het f+b x5a2)total volume $3900\,cm^3$ contains $3600\,cm^3$ of air and $3300\,cm^3$ of water at a temperature of $27^{\circ}C$. The system is cooled and the piston contracts at constant pressure.
What is the approximate total piston volume at the point where the water first starts to freeze?
A. 273$cm^3$
B. 546$cm^3$
C. 819$cm^3$
D. 846$cm^3$
