Вставьте is или are: 1. cold — in — it — winter — is. 2. work — to — is — it — hard — necessary. 3. English — it — difficult — to — is — in — write. 4. interesting — read — it — to — books — is — English. 5. often — it — in — rains — autumn. 6. get up — is — too — to — it — early. 7. do — exercises — to — is — important — it. 8. it — cold — is — winter — in? 9. necessary — to — revise — it — is — grammar — rules? 10. easy — is — write — to — it — in English? 11. watch — it — useful — to — is — television? 12. go — bed — is — early — to — it — to? 13. it — snow — winter — often — does — in? 14. does — rain — it — when — often? 15. pleasant — stay — is — it — not — to — in town — in summer. 16. snow — does — in — not — summer — it. 17. speak — without — it — English — not — to — is — easy — mistakes. 18. smoke — useful — is — to — it — not.

1. It is cold in winter.
2. It is necessary to work hard.
3. It is difficult to write in English.
4. It is interesting to read English books.
5. It often rains in autumn.
6. It is too early to get up.
7. It is important to do exercises.
8. Is it cold in winter?
9. Is it necessary to revise grammar rules?
10. Is it easy to write in English?
11. Is it useful to watch television?
12. Is it early to go to bed?
13. Does it often snow in winter?
14. When does it often rain?
15. It is not pleasant to stay in town in summer.
16. It does not snow in summer.
17. It is not easy to speak English without mistakes.
18. It is not useful to smoke.

В предложениях 1–12, 15, 17–18 используется формальное подлежащее it с формой is; в предложениях 13, 14 и 16 смысловой глагол в вопросах и отрицании употребляется с does.