The guest molecule which will fit best inside α-cyclodextrin by interacting with both, rim and cavity, is

Concept:

• The chain conformation of D-glucose is responsible for the formation of three native cyclodextrins (CD's), these are α-CD, β-CD, and γ-CD.
• The Schematic representations of CD's are shown below:

• The polar exterior of cyclodextrins (CD's) is known as rim, and can interact with polar functional groups. The interior cavity is hydrophobic as it is lined with non-polar groups, and can interact with non-polar groups.
• The hydrophobic cavity of CD's has the ability to encapsulate, either partially or fully, small organic molecules.
• The hydrophobic cavity of α-CD's is the smallest in size. 

Explanation:

• Cyclodextrins (CD's) can form complexes with a wide range of molecules including branched or cyclic alkyl groups, aromatic molecules, and proteins.
• Interactions between cyclodextrins (host) and guest molecules yield a stable complex with a high equilibrium constant.
• The α-CD can interact with the guest molecule "C" through H-bonding in the exterior (rim). While the hydrophobic cavity can interact with the non-polar part of the guest molecule.

Conclusion:

Hence, the guest molecule which will fit best inside α-cyclodextrin by interacting with both, rim and cavity, is