Необходимо правильно, учитывая времена раскрыть скобки. Помогите, пожалуйста! Historians...

Question

Необходимо правильно, учитывая времена раскрыть скобки. Помогите, пожалуйста!

Historians tell us that the problem of pollution (1) … (to exist) even in
ancient Troy, but it (2) … (to be) very simple. The citizens of ancient Troy
(3) … (to allow) their refuse to accumulate on the floor until there was
such an amount that their doors would not open. Then they simply (4) …
(to reposition) the doors.
The decrees issued to decrease pollution (5) … (to record) as long ago
as the Middle Ages. In England, smoke-abatement law (6) … (to pass) in
1273, and in 1306 a man (7) … (to execute) for burning coal.
However, the Industrial Revolution changed all prior concepts of pollution.
The introduction of power-driven machinery created a pollution
problem that (8) … (to increase) steadily from the mid-eighteenth century
to the present time. The results of industrial pollution (9) … (to be) water
and air toxification, respiratory diseases, and even death. That (10) …
(to prompt) the Environmental Protection Agencies to establish laws to
regulate levels of air and water pollution.

Answer 1

Historians tell us that the problem of pollution (1) … existed even in
ancient Troy, but it (2) was very simple. The citizens of ancient Troy
(3) to allowed their refuse to accumulate on the floor until there was
such an amount that their doors would not open. Then they simply (4) …
repositioned the doors.
The decrees issued to decrease pollution (5) were recorded as long ago
as the Middle Ages. In England, smoke-abatement law (6) …was passed in
1273, and in 1306 a man (7) was executed for burning coal.
However, the Industrial Revolution changed all prior concepts of pollution.
The introduction of power-driven machinery created a pollution
problem that (8) increased  steadily from the mid-eighteenth century
to the present time. The results of industrial pollution (9) are  water
and air toxification, respiratory diseases, and even death. That (10) …
prompted the Environmental Protection Agencies to establish laws to
regulate levels of air and water pollution.