Which of the following types of decoration was often used in Italian churches during the middle ages?

I think the primary was stain glass. It was seen as the light of God and it was a way for the church to educate the people about the bible. People couldn't read but they could interpret the stories in glass. Then, the next was the flying buttresses and the statuary. Not to mention the fresco's . All of this worked together for a special space full of light and color like nothing else in the middle age world. Seeing these today is still an awe inspiring experience.