Bonjour,
Réponse :
1. Mr. Clever, as his name suggests, is very intelligent.
2. Little Miss Chatterbox always keeps her phone in her handbag
3. Mr. Happy and Mr. Cool, as their names indicate, are very good company
4. Mr. Messy doesn't like to tidy his room.
Explications :
his : son /sa /ses ( possesseur masculin )
her: son/sa/se ( possesseur féminin )
their : leurs ( leur/leurs )