Select all the possible reasons for why the temperature in the ideal gas formula must be given in an absolute temperature scale:
a. There is no motion at absolute zero.
b. Absolute zero must be the temperature at which the gas pressure is equal to zero.
c. If the temperature scale used in the ideal gas equation can take negative values (such as Celsius), then the ideal gas equation will permit negative pressures and that does not make sense.
d. The Kelvin is not only a temperature scale but a measurement unit.
