名词变复数：shelf cherry
shelves cherries
名词变复数：zoo watch
zoos watches
名词变复数：leaf box
leaves boxes
名词变复数：knife boy
knives boys
名词变复数：piano library
pianos libraries
名词变复数：day tomato
days tomatoes
名词变复数：rose city
roses cities
名词变复数：book brush
books brushes