다음 글의 주제로 가장 적절한 것은?


The rise of cities and kingdoms and the improvement in
transport infrastructure brought about new opportunities for
specialization. Densely populated cities provided full-time
employment not just for professional shoemakers and
doctors, but also for carpenters, priests, soldiers and
lawyers. Villages that gained a reputation for producing
really good wine, olive oil or ceramics discovered that it
was worth their while to specialize nearly exclusively in
that product and trade it with other settlements for all the
other goods they needed. This made a lot of sense.
Climates and soils differ, so why drink mediocre wine from
your backyard if you can buy a smoother variety from a
place whose soil and climate is much better suited to
grape vines? If the clay in your backyard makes stronger
and prettier pots, then you can make an exchange.


① how climates and soils influence the local products
② ways to gain a good reputation for local specialties
③ what made people engage in specialization and trade
④ the rise of cities and full-time employment for professionals