  Two important problems existing in Tsallis' statistics are investigated,
where one is whether energy is extensive or not, and the other is whether it is
necessary to introduce the so-called generalized zeroth law of thermodynamics
or not. The results obtained show clearly that like entropy, energy is also
nonextensive in Tsallis' statistics, and that the zeroth law of thermodynamics
has been implicitly used in Tsallis' statistics since 1988. Moreover, it is
expounded that the standard energy additivity rule adopted by a great number of
researchers is not suitable in Tsallis' statistics, because it not only
violates the law of energy conservation but also its corollary is in
contradiction with the zeroth law of thermodynamics.
