What did the practice of containment mean? apex?

The sahel is located on the edge of the sahara desert. a.north b.west c.south d.east

Which of the following is an example of the pull factor known as economic migration? a. better educational opportunities pulling people towards a new country b. mexican laborers entering the us to work in agricultural jobs c. joining family members that are already in a new country d. crop failures driving people away from their country i am unsure on this question, i was thinking b? but i could be wrong.

Which best describes the impact of the crusades on european exploration?