The trolleys have been reduced over the last decades, after their initial increase as a public transportation, when new and better ways were discovered/produced for transport, their decline has started.
The buses since their invention, had grown in number and became a very important part of every city's public transportation, and still are.
The rapid transit is the most recent one of the mentioned in here. It's popularity has grown, number increased, and is very practical because it is not causing traffic mess. It is very important transport asset nowadays and makes lives of millions of people much easier.
The soviet Union is primarily responsible for the pollution in the region of Central Asia. The correct option among all the options that are given in the question is the first option. The Soviet Union is one country that depends highly on coal based electricity generation. These power stations release toxic gases that are a reason for global warming.
