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.