1. wifes, bread(нельзя), mice, sons-in-law, heroes, piano(нельзя), handkerchiefs, sheep(исключение), Universities, money(искл), libraries, flies, bushes, thieves, men, geese, children, postmen, passers-by.
2. 1the books; 2feet; 3the knives; 4laboratories; 5the roofs of the houses WERE covered...; 6news всегда пишется с S на конце, но всегда в ед.числе(The news IS good); 7advices...WERE good; 8furniture всегда в единственном; 9fruit всегда в единственном; 10There're sheep...; 11Are there workers Englishmen or Germans?;12There hotels are... but they're very nice; 13These cups are dirty; 14Those biscits were tasty.
И, наконец,3
Helen's and Nick's car
The bird's nest
Roof's house
Kate's new dictionary
Stidents' book(Если мн.ч - апостроф после s)
Chilrden's toys
My brother-in-law's library
Month's holiday
Ship's crew
Moscow thertres
Today's conversation
My friend's office