(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

