The National Trust There are lots of beautiful, large houses in Britain. Many of them (1) were built hundreds of years ago. In the past, they (2) were owned by very rich families. Today, many of them (3) are owned by an organization called The National Trust, which (4) was created to look after them. The houses (5) are kept in perfect condition, and visitors (6) are allowed to look round them. It's interesting to learn how different life was in an old house. Milk was (7) not kept in the fridge, because they didn't have fridges! Washing machines (8) were only invented very recently, so washing (9) was done by hand. In some cases, the house (10) is still lived in today. When this happens, visitors (11) are only shown part of the house. The private rooms (12) are kept closed to the public. These houses often have beautiful gardens, too. The gardens (13) are looked after by professional gardeners. You usually have to pay to look round National Trust houses. Members of the National Trust (14) are given a discount. This year, millions of people (15) will be given the chance to see what life in an old country house was like.

Вот разбор всех форм в тексте — что это за времена/конструкции, от какого глагола образованы и почему употреблён пассив:

1. were built — Past Simple Passive от build. Речь о факте в прошлом; кто строил, неважно/не назван.

2. were owned — Past Simple Passive от own. Подчёркивается состояние владения в прошлом, а не действующее лицо.

3. are owned — Present Simple Passive от own. Текущее положение дел: сейчас дома принадлежат организации.

4. was created — Past Simple Passive от create. Исторический факт об основании организации.

5. are kept — Present Simple Passive от keep. Регулярное/обычное действие: дома поддерживаются в идеальном состоянии.

6. are allowed — Present Simple Passive от allow. Общее правило: посетителям разрешают осматривать дома.

7. was not kept — Past Simple Passive (отрицание) от keep. Про прошлые реалии: молоко не хранили в холодильнике.

8. were only invented — Past Simple Passive от invent. Изобретатели не важны; важен факт изобретения в прошлом.

9. was done — Past Simple Passive от do. «Washing» — подлежащее (стирка), действие совершалось вручную.

10. is still lived in — Present Simple Passive от фразового live in. Пассив с предлогом на конце («предложный пассив»): в доме всё ещё живут.

11. are only shown — Present Simple Passive от show. Правило для посетителей: показывают только часть дома.

12. are kept closed — Present Simple Passive от keep + объектный комплемент closed (сохраняются закрытыми).

13. are looked after — Present Simple Passive от фразового look after. Уход осуществляется профессионалами.

14. are given — Present Simple Passive от give. Общее правило: членам дают скидку.

15. will be given — Future Simple Passive от give. Будущее: людям предоставят возможность.

Общее правило образования пассива: be + V3 (past participle), где форма be меняется по времени (was/were, is/are, will be и т. д.). В английском пассив удобен, когда действующее лицо неважно, неизвестно или очевидно из контекста, а на первый план хотят вывести сам объект/факт действия. Здесь это и происходит: фокус — на домах, правилах посещения и фактах из истории, а не на конкретных исполнителях.