Fill in the blank with a suitable preposition.
Van Gogh's painting was hung _______ Claude Monet's painting in the gallery.
The prepositions ‘below’ and ’under’ mean lower than something, but we prefer ‘below’ when something is not vertically or directly under something else or covered by something. In such situations ‘under’ is preferred since it expresses that an object or person is literally lower than something else. In the given sentence the painting can only be ‘below’ another painting because paintings don't cover or lay on top of one another. Therefore option A is right, while option B is incorrect. On the other hand, ‘on’ and ‘upon’ are both used to speak about something being on top of a surface or object. One painting cannot be on another painting; hence options C and D are incorrect.