Образовать множественное число: boot , ox, fox, wom¬an, mouth, mouse, goose, deer, ship, sheep, crisis, nucleus, formula, room-mate, man-of-war, boy-messen¬ger, passer-by.

boot - boots, ox - oxen, fox - foxes, woman - women, mouth - mouths, mouse - mice, goose - geese, deer - deer, ship - ships, sheep - sheep, crisis - crises, nucleus - nuclei, formula - formulas /formulae, room-mate - room-mates, man-of-war - men-of-war, boy-messenger - boy-messengers, passer-by - passers-by.