Ответ:
can, may, must, need.
1 Peter need return the book to the library. 2 Why can not you understand it? It is so easy. 3 can
we do the exercise at once? – Yes, you must do it at once. 4 may I take your pen? – Yes,
please.5. Shall I write a letter to him? – No, you need not, it is not necessary. 6 When can you
come to see us? – I can come only on Saturday.
Объяснение: