Iv.поставьте существительные во множественное число, распределив в зависимости от звучания суффикса ([s], [z], [iz], исключения): student, factory, hero, bush, play, tooth, knife, church, fire-company, showgirl, fireman, child, boy, lamp, computer, fox, clock, bed, flower, niece.

[s] - students, lamps, clocks
[z] - factories, heroes, plays, knives, fire-companies, showgirls, boys, computers, beds, flowers,
[iz] - bushes, churches, foxes, nieces
исключения - teeth,  firemen, children,