If a city wants to build a garden or build a pond, there are the following four assumptions: a bridge is needed to build a pond; a garden cannot be built when a bridge is built; a tree must be planted to build a garden;. Based on this it is impossible to introduce:. ['Finally, there is a pond.', 'There must be a bridge in the end.', 'There may be a garden in the end.', 'Pond and garden cannot exist at the same time.']