U - 4 combinations
619. ufo = airplane + alien, alien + container, alien + rocket, alien + sky, alien + space station, alien + spaceship
620. umbrella = fabric + rain, fabric + storm, rain + tool, storm + tool
621. unicorn = double rainbow + horse, horse + legend, horse + magic, horse + rainbow, horse + story
622. universe = galaxy cluster + galaxy cluster, container + galaxy cluster, container + space