What in one way which the relationship between Muslims and Christians worsened?

Relations among Muslims, Jews, and Christians have been shaped not only by the theologies and beliefs of the three religions, but also, and often more strongly, by the historical circumstances in which they are found. As a result, history has become a foundation for religious understanding.

Explanation:

In each historical phase, the definition of who was regarded as Muslim, Jewish, or Christian shifted, sometimes indicating only a religious identification, but more often indicating a particular so­cial, economic, or political group.

your answer would be (a)

b. great plains

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