3. Build the plural form from following nouns: Pen, window, wall, week, clock, ship, library, watch, dress, country, glass, day, party, play, bus, leaf, life, colony, hero, fox, half, Negro, mass, eye, language, place, shelf, key, roof, thief, ray, bush, mouth, journey, man, woman, tooth, foot, goose, child, mouse, postman, son-in-law, fisherman, schoolgirl, sister-in-law, text-book, pocket-knife, passer-by, statesman, editor-in-chief.