Write the plural of the following nouns : Piano , shelf , army , potato , safe , wolf , cliff , wife , schoolboy , schoolchild , leaf , life , factory , knife , man , roof , photo , toy , tomato , class , room , copy , book , note , house , wife , news , paper , home , land , mother , country , student , typist , writer , pilot , doctor , officer , architect actor , actress , painter , sailor , dentist , teacher , mechanic , locksmith , driver , composer shop - assistant .​