Поставьте следующие группы слов: а) во множественное число: a duty., a mouse, an exercise, a watch, a judge, a leaf. b) в единственное число: women, boys, shelves, teeth, libraries, boxes

1) A duty - duties, a mouse - mice, an exercise - exercises, a judge - judgies, a leaf - leaves, a watch - watches.
2) Women - woman, boys - boy, shelves - shelf, teeth - tooth, libraries - library, boxes - box.