One ton of the refrigeration is_________________?

A. the standard unit used in refrigeration problems
B. the cooling effect produced by melting 1 ton of ice
C. the refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours
D. the refrigeration effect to produce 1 ton of ice at NTP conditions
E. the refrigeration effect to produce 1 ton of ice in 1 hour time