Ex. 2. Give the plural of the following nouns. Wife, stepmother, father-in-law, safe, workbook, sister-in-law, dictionary, teapot, mouse, brush, parking space, watch, toe, city, hero, piano, calf, cliff, proof, chief, stitch, bath, bell, life, shelf, berry, valley, roof, pen, window, wall, ship, library, bus, colony, eye, language, thief, key, ray, mouth, foot, boot, ox, fox, woman, goose, cheese, deer, sheep, crisis, phenomenon, datum, nucleus, basis, apparatus, criterion, series, analysis, formula, room mate, fellow-worker, man-of-all, onlooker, passer-by, fisherman, editor-in-chief.

Wives, stepmothers, fathers-in-law, safes, workbooks, sisters-in-law, dictionaries, teapots, mice, brushes, parking spaces, watches, toes, cities, heroes, pianos, calves, cliffs, proofs, chiefs, stitches, baths, bells, lives, shelves, berries, valleys, roofs, pens, windows, walls, ships, libraries, buses, colonies, eyes, languages, thieves, keys, rays, mouths, feet, boots, oxen, foxes, women, geese, cheeses, deer, sheep, crises, phenomena, data, nuclei, bases, apparatuses, criteria, series, analyses, formulas, rooms mates, fellow-workers, men-of-all, onlookers, passers-by, fishermen, editors-in-chief.