Answer:
The verb "stocker des choses" (to store things) is most commonly associated with the room la cave (the cellar). So the answer is:
stocker des choses -> la cave
Step-by-step explanation:
The other rooms in the list are associated with different actions:
le garage (the garage): garer une voiture (to park a car)
la salle de séjour (the living room): regarder la télévision (to watch television)
le jardin (the garden): planter des fleurs (to plant flowers)
la chambre (the bedroom): dormir (to sleep)
la salle à manger (the dining room): manger (to eat)