Образуйте во мн. ч. cheese, child, crisis, room, fellow, time, formula, class-mate, mother-in-law, man, student, tooth,

Cheese – cheese (cheeses), child - children, crisis - crises, room - rooms, fellow - fellows, time - times, formula - formula,  classmate – classmates, mother-in-law – mothers –in law, man - men, student - students, tooth - teeth, people - people, figure - figures.