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(a) The host (H), the guest (G), and their “reduced” derivatives (H′ and G′); G′ is not caged by H′. (b) When G′ is not caged by H′, there might exist some host (H̃) and guest (G̃) models obtained from H and G by the constrained shift of their balls such that G̃ is not caged by H̃. (c, d) Same as (a, b) except that G′ is caged by H′; in this case, any G̃ is also caged by H̃.
