<span>The pope required that the monarchs make them convert to Christianity.</span>
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 subject of science is very broad. With that being said, I think there is no official regulatory board that decides the branches of science. Scientific developments are products of joined efforts of different scientists. These scientists could rebuke another's work provided there is evidence. As long as the theory is generally accepted by the scientists and no one rebukes it effectively, then it is a generally accepted fact and everyone adapts it.
Hence, the answer is B.
