The words that are missing in the sentence are The Second Great Awakening and moral renewal. The so-called Second Great Awakening is referring to revival of religious during the early nineteenth century, where the preachers are advocating or sharing the message of spiritual and moral renewal to people.
The correct answer is Indus.
The Yellow River was an important part of Chinese civilization.
The Tigris River was an important part of the Mesopotamia civilization, located in modern day Iraq.
The Amazon River is located in South America, and was an important part of several different civilizations.
This shows that the only correct answer can be Indus River.
