Tenacious qualities necessary for a historian
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.
Black slaves who wgere imported from africa
Learned behavior
This is because instinct drives them to eat and find food, but they have to learn that a certain feeder is always out and available
Explanation:
You can try to think of it as a picture in your head.
