Поставьте глагол в скобках в соответствующую видовременную форму (страдательный залог). переведите предложения. solutions of ecological problems may (achieve) by join efforts of all countries. the worst environment pollution (cause) by the manufactures who put chemical wastes into rivers and seas. the problem of the ozone layer (discuss) when i came. the construction of the cleaning installation (finish) by the end of the last year. environment problems (solve) if we learn to live in harmony with nature.

Solutions of ecological problems may be achieved by joining ef­forts of all countries. 
The worst environment pollution is caused by the manufactures who put chemical wastes into rivers and seas. 
The problem of the ozone layer was being discussed when I came. 
The construction of the cleaning installation had been finished by the end of the last year. Environment problems will be solved if we learn to live in harmony with nature.