Choose one of the two forms:
1. Our school gets ... (hundred, hundreds) of letters every year.
2. Five ... (hundred, hundreds) new houses were built in our city last year.
3. You can see (million, millions) of stars in the night sky.
4. Six ... (million, millions) tourists visited Rome last summer.
5. Our library has received four ... (thousand, thousands) new books.
6. ... (thousand, thousands) of pupils nowadays try to learn two foreign languages.