Answer:
(4) European involvement in the Crusades
Step-by-step explanation:
The other points which are given in the question are the situations which had happened because the Europeans had involved them selves in the crusades.
The effects of this involvement was the development of the middle class in the society. It also led to the increase in the demand of the eastern goods by the people of Europe.
More over the people of Europe had developed new interest in learning. All this had happened because the Europeans had involved themselves in the crusades.