Which sentence uses put up to mean mount or erect something?
The volunteers put up a shelf in the tool room.✓Bonne réponse
The volunteers put together a shelf on the floor.
The volunteers put the boxed shelf away in storage.
The volunteers put a spare shelf aside for another room.
Explication
Mounting a shelf on a wall is expressed by putting it up, because the object is fixed in position for use. Putting a shelf together would assemble its pieces but would not establish that it was mounted on the wall.