填空题

New York is one of the (11) large American cities to have. some of its policemen on horseback. The New York Police have 170 horses that they use in certain parts of the city. The horses are expensive to (12) , but it needs even more special horseshoes. In fact, they need more than (13) of them each year. Every police horse in New York gets new shoes every month. (14) these shoes in good repair is the job of six black-smiths. There are only about thirty-five of these blacksmiths in the (15) United States.