= Solution
At fixed positive <pressure>, the extrapolated term $C_{mp}\ln(T/T_0)$ tends to \b[$-\infty$] as $T\to0^+$. That prediction is \b[not physically realistic] for an equilibrium sample. The classical ideal-gas description with constant <heat capacity> cannot extend unchanged to absolute zero. A real substance generally undergoes phase changes, and <quantum statistics> and thermal freeze-out change its <heat capacity> and <entropy>. For a nondegenerate equilibrium <ground state>, the third law gives <entropy> approaching zero; residual ground-state degeneracy can give a finite residual value rather than this negative <divergence>. This is a breakdown of the extrapolation, not a violation of the third law by a real gas.
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